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This Month's Featured Story

The Colorful Salt Mines of Belarus

Belarus's Salt Mine Tunnel

Multicolored walls of a salt mine located 1,380 feet (420 meters) underground, near the town of Soligorsk, south of Minsk, Belarus. Parts of this mine have been converted into a speleotherapy clinic for treatment of respiratory illnesses such as asthma and bronchitis.

Opened in 1949, this mine was notable for its salt, which containes high levels of potash (salts that contain water-soluble potassium). One of the five excavation chambers opened here in the last 50 years is still in use to collect minerals, but the rest have been transformed for halotherapy, or salt therapy. It is believed that the dry air charged with salt ions has a positive chemical effect on the respiratory system. Many patients who come here for treatment are children from the regions of affected by the Chernobyl disaster, but patients travel from countries like Russia, Japan, and Ukraine to receive treatments. The mine is only open to patients and staff in order to avoid disturbing the treatments.

Salt deposits in Soligorsk, are visible long before the entrance to the city. Salt mining in Soligorsk has been carried out since the 1950s on one of the largest deposits in Europe. Dumps of red color with dazzling white impregnations of salt create an extraterrestrial landscape, which is supplemented by mud sinks and artificial lakes. The wonderful colors are a natural occurrence caused by evaporation zones, sediments, and the mineral carnilite, which forms after a salty sea, dries up, leaving behind the different colors of the same mineral. 

 

To visit this place you would need a special permit.

Belarus's Salt Mine

Photographer Viktor Lyagushkin ventured into Berezniki, Belarus's sylvinite mine to photograph the psychedelic underground world.

Previously Featured

Did the Holy Grail of the modern world just get invented? Well, maybe not invented, but found by using a lead phosphate apatite mineral? Replace a few lead atoms with copper and viola! We wanted to get this in front of you becasue it seems very promising and if its true, it will change the world and transform how we use energy very soon. Not only does this change materails science and transform our energy hungry society, it could lead to other inventions that could quickly change the world!

Please watch this to the end; there's quite a bit of ground that it covers, and the explanations are well done, so it's worth a good watch. This little black rock floating on the magnet is an amazing scientific find. Once again, minerals have changed the world!

For our January story, we're featuring two minerals in a head-to-head shoot-out of chemistry and qualities. These two are very similar in name and often confuse collectors just by the name alone.
So what's it gonna be? 

Stibnite vs Stilbite
While both minerals have very different appearances, remembering their names often trips people up. They are visually very different and do not share any common chemistry, nor are they found together.

Stibnite

Formula: Sb2S3 - An Antimony Sulfide

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  • An important Antimony ore

  • Used in ancient times as an eyeliner.

  • It is named after the Latin name for the element Antimony.

  • Comes in around 2 on the Mols hardness scale.

  • Also known as antimony glance, antimonite, and stibine.

  • It has a gunmetal metallic luster, very much like Galena.

Stibnite occurs in hydrothermal deposits and is associated with realgarorpimentcinnabargalenapyritemarcasitearsenopyritecervantitestibiconitecalciteankeritebarite and chalcedony. Small deposits of stibnite are common, but large deposits are rare. The world's largest deposit of antimony, the Xikuangshan mine, yields high-quality crystals in paragenesis with calcite. It occurs in CanadaMexicoPeru, JapanGermanyRomaniaItalyFranceEnglandAlgeria, and KalimantanBorneo. In the United States it is found in ArkansasIdahoNevadaCalifornia, and Alaska.

Romanian Stibite

Stibnite from Romania. Image provided by Wikipedia Commons.

Stilbite

Formula: NaCa4(Si27Al9)O27•28H20 - A Zeolite

Stilbite-Ca-251147.jpg
  • As a Zeolite, Stilbite can be used in industrial filtering processes.

  • Named in 1797 after its glittery shine or "stilbe".

  • Comes in around 3.5 to 4 on the Mols hardness scale.

  • Its customary shape and nodules are often described as looking like cauliflower.

  • Its color can vary between white, creamy, light yellow, light grey, and pinks to orangy-red.

At one time heulandite and stilbite were considered to be identical minerals. After they were found to be two separate species, in 1818, the name desmine ("a bundle") was proposed for stilbite, and this name is still employed in Germany. Stilbite shows a wide variation in exchangeable cations. Since silicon and aluminium have a different charge (Si4+ and Al3+) the ions occupying the sodium/calcium site have to adjust to maintain charge balance. There is a continuous series between stilbite and stellerite, Stilbite crystals are typically thin tabular, flattened parallel to the dominant cleavage, and elongated along the a-axis. Aggregates may be sheaf-like or in bow-ties, also fibrous and globular.  Twinning, cruciform, and penetration, is extremely common

Stilbite & Fluorapophyllite

Stibnite (yellow-orange color, with Fluorapophyllite (greenish color) on white or clear Stilbite from Maharashtra, India. Image provided by Wikipedia Commons.

An Amethyst story

Article Adapted from: https://flipboard.com/video/businessinsider/92b68af35f

Originally Written by Business Insider

How miners find, cut, and transport the most expensive amethysts in the world!

Amethyst is one of the most abundant crystals in the world. But the most prized pieces can cost almost a million dollars. Some of the world's largest amethyst geodes come out of Artigas, Uruguay. The earth beneath this region is uniquely suited to producing amethyst. But other than size, what qualities do miners look for in a valuable amethyst? And how are the crystals prepared once they're out of the ground? We explored why amethyst geodes are so expensive.

Ulexite

The Amazing Fiber Optic Mineral

Article Adapted from: https://rockseeker.com/ulexite/

Originally Written by Jeremy Hall

Ulexite is a strange, fibrous mineral with some interesting optical properties. It’s sometimes referred to as television stone, owing to the strange visual properties that it carries. It’s a complex matter and one that takes a bit of study to figure out. So, without further ado, let’s break in with our guide to ulexite, and see if we can’t shed some light on this fascinating mineral.

California Ulexite

What is Ulexite?

Ulexite is a boron mineral, specifically hydrated sodium calcium borate hydroxide (NaCa[B5O6(OH)6] · 5H2O). It appears as bundles of transparent fibers tightly “bound” together. Boron is a very rare element, found in high concentrations in only a few places across the planet. It’s also used in a surprising amount of processes that are essential to our modern lifestyle. For instance, borosilicate glass is preferred over other types when heat or thermal shock may be an issue since it resists both of those quite well.

You probably have some borosilicate glass in the kitchen; it’s generally called Pyrex. Boron is never found in its elemental form in nature. Instead, it’s found in a wide range of different minerals. Many of these are of commercial importance, but the three main sources of boron for industrial use are ulexite, borax, and colemanite. Boron is also used to harden steel when added to alloys. Overall, it’s useful stuff even when it’s not of interest to mineral collectors. Ulexite is a standout option due to occurring in relatively large amounts when found and being easy to process in order to liberate the boron molecules for use. Ulexite is also being explored as a starting medium for sodium borohydride. This compound is thought to be an ideal storage mechanism for hydrogen fuel cells due to its high weight-to-hydrogen ratio.

Ulexite Slab

Where Can You Find Ulexite?

Ulexite is most often found in evaporite deposits. Evaporite deposits are known to contain many boron minerals, from howlite to ulexite, and also contain things like halite, gypsum, and calcite. These minerals are all soluble in water to some extent. Essentially, these deposits were thrown from volcanic activity, termed pyroclastic, which contained boron. Water flowed over these stones and to lower ground, slowly removing minerals from the stones. These include boron minerals, such as borax and ulexite. ​Because of this, you’ll want to make sure that you don’t expose any ulexite samples you have to water. Hot water, in particular, will dissolve or damage your sample. If you do need to rinse dust or dirt off of a specimen, it’s best to use a rag that’s been made damp with cold water.

 

In general, you’ll find evaporite deposits in dry lakes. A dry lake is one that fills up with water during the rainy season but loses water quicker than it gains it. This results in the lower ground being encrusted with salts picked up from the pyroclasts. Over time, these can often form into a stratum. A stratum is a specific layer of stone, so an area with large amounts of boron will often end up with layers comprised entirely of borate beneath the surface.

The most prevalent source of the material is the Boron Pit in Boron, California. Unfortunately, you’re probably not going to be able to collect from this area. While there is an area farther down the mountain where the tailings are dumped, this is both not allowed and incredibly dangerous. The Boron Pit is actually the world’s largest borax mine. It’s a pit mine with an enormous circumference and 755 feet or so deep. However, the mineral isn’t hard to acquire. A single individual, David Eyre of Desert Discoveries has an exclusive contract to collect the optical grade ulexite which is removed from the mines owned by Rio Tinto. Fortunately, optical ulexite is widely available online if you really want to own a piece of this natural oddity.

Ulexite "TV Rock"

Photo Credit: Minerals.net

Ulexite Sample from Mindat

Ulexite Slab from Mindat.org

The "TV Stone"

Ulexite is often called the “TV Stone” due to its strange optical properties. The fibrous form of the mineral transmits light somewhat like a fiber optic cable. When cut across these fibers, it can transmit an image clearly. This is incredibly rare with natural minerals, the only other one known to do so is fibrous selenite. Selenite, however, does not transmit nearly as clear of an image. Keep in mind that this is different than the mineral simply being transparent, instead, the image is actually projected onto the surface of the ulexite. The internals of these fibers are perfectly reflective. The fibers themselves are about 2 micrometers across. This only works when the fibers are parallel to the image you’re trying to project. If you rotate the stone 90 degrees it no longer displays the properties. Large samples of ulexite in this form are vanishingly rare. The problem is the same as the reason it forms. Quite often you’ll also find mud or other inclusions that were trapped during the formation of the mineral. These can obscure the view and render it more fit for industrial use than demonstrating its natural fiber optic qualities. Pieces a few inches across are common finds on any site that sells minerals, and for many people, this may be the only way to collect it.

"Bunny Tail" Ulexite

Ulexite is sometimes found in a form that resembles a cotton ball. You’ll also see this form referred to as “bunny tails” in some places. These are actually comprised of small, needle-like crystals. While an interesting specimen, people are generally more interested in finding the larger masses of fibrous crystals since the tufts can’t be worked into a form that shows off the unusual characteristics of the mineral. That said, the acicular form can make for incredible specimens. This form is very fragile, however, and care must be taken when searching for it. They generally grow in hollows in the bedrock. The acicular formations may be found singly, or in overlapping patterns. Some of these can be quite dramatic in effect. Unfortunately, this form is also hard to find for sale since there’s not much demand for it.

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The Amazing World of Trilobites

A Brief History of Trilobite Shapes and Ecology...

Adapted from "The Colorful World of Trilobites" by Pete Buchholz and Franz Anthony

The fossils of small-segmented animals had been known to humans for centuries, but for most of that time, no one was really sure what they actually were. Their durable armored exoskeleton and habit of molting ensured that they were easily fossilized and discovered by people hundreds of millions of years later. Some Native American people used Elrathia fossils as amulets and back in 1679 the first scientist to study Ogygiocarella thought it was a flatfish skeleton.

          Trilobite fossils are far more than small bumpy black fossils that scuttled around on the ocean floor. They can be found all through the ancient oceans of the earth and even ventured on land near the beaches. They evolved their own unique excellent eyesight that they used to find food and even hunt. It's very likely that they came in a host of colors like today's crustaceans.

          Throughout the 18th century, many new fossil species were discovered, confounding scientists about their identities. Their segmented bodies and compound eyes reminded scientists of insects and crustaceans, offering clues to their true identity. By the dawn of the 19th century, these fossils, now known as trilobites, were considered to be quite like crustaceans, but not exactly. They were unique among known animals with no living examples.

trilobites_ea-2.jpg

Image (Left to Right): Fallotaspis, one of the oldest trilobites from the group Redlichiida, the 'stealth bomber' Lonchodomas, and the upside-down Carolinites. Image by Franz Anthony.

Although they have a lot of anatomical diversity, trilobites all follow the same basic body plan. They’re divided into three lobes; the left, right, and center. They also have three main body sections, a head, several torso segments, and a tail, with some having a long tail spine. These features make them easy to identify for amateur fossil hunters.

Trilobite Diversity

As the Paleozoic progressed trilobites pushed their limits, moving into new environments. Trace fossils of tunnels, called Cruziana, were formed by trilobites digging under the surface. There are footprints of trilobites walking on the sandy upper beach of an ancient shore at low tide. They were among the first animals to ever venture out of the seas, even if it was just for a few minutes. Some species ventured into the deep sea, becoming completely blind where daylight never penetrates.

          They are famously segmented and are part of a huge lineage of animals with segmented legs and bodies known as arthropods. That lineage also includes insects, crustaceans, millipedes, spiders, scorpions, and many others. Trilobites may look a lot like some living arthropods like horseshoe crabs or pill bugs, but they are only distantly related to them, and were one of the earliest arthropod groups to emerge.

          In their time, the humble trilobites filled roles today occupied by crustaceans. They didn’t just fill in for the crabs scuttling along the bottom, but shrimp swimming in the water and digging in the sand, and even filling the roles of many living fish like catfish and small sharks.

Armored Shells

The fossils we find are normally just the upper halves of trilobites. Their upper parts were strengthened with calcite like the shells of crustaceans, but their legs and bellies were armored only with stiff proteins that usually decomposed before fossilizing. Many trilobites were covered in defensive spines and barbs as a way to protect themselves from being eaten. Others, like Phacops, evolved a defense mechanism later copied by pill bugs and armadillos: rolling into a ball. Many specimens of enrolled trilobites record their final fight for survival.

Calcite Eyes

The earliest trilobite eyes are known as holochroal and had densely packed lenses, with a single corneal layer covering the whole eye. The vast majority of trilobites have holochroal eyes, but not all of them. A lineage of trilobites known as the phacopids evolved a modified type of compound eye called schizochroal, where each calcite lens is separated from its neighbors by exoskeletal tissue and each has an individual cornea. Schizochroal eyes resemble the eyes of young trilobites with holochroal eyes that may have been the result of paedomorphosis, the retention of juvenile features in adult animals. Some trilobites grew eye stalks so they could see 360 degrees in every direction, or even used their eyes like a periscope while buried under the sand.

Diet and Food

Trilobites had mouths on the bottom of their heads and like their insect and crustacean cousins had numerous complex mouthparts to help them eat. Like insects and crustaceans, they also had diverse diets. Some ate algae, while others, like Scotoharpes and kin, may have been specialized filter feeders. Many ate dung and detritus while others were carnivores, some even feeding on smaller trilobites.

Antennae, Legs & Colors

The highly mobile, visually oriented, and social animals came in all kinds of shapes and sizes, behaviors, and surely colors and color patterns. Their rarely fossilized antennae and legs emerged from under their shield-like shells, and allowed them to move, interact, and behave like fully competent creatures. Rare specimens tell the rest of the story, with curving antennae emerging from under the head, and one set of legs and gills for each torso segment.

          Specimens of a trilobite called Eldredgeops even had freckles of calcite crystals on their back, rare evidence of a color pattern that the animal sported in life. The spots might have been used as a form of camouflage, blending in with the sandy bottoms to avoid predators.

trilobites_ea-3.jpg

A selection of trilobites, illustrated in bright colors inspired by today's crustaceans. 

 

Image (Left to Right): Triarthrus, the first trilobite known with legs and even eggs preserved; Miraspis, a spiky trilobite with eyestalks; and Eldredgeops, a trilobite with calcite crystal spots on its back. Image by Franz Anthony.

Trilobite Fossils and Illustrations Today

Some spectacular trilobites were fossilized with pyrite, also known as “fool’s gold.” They are the brilliant metallic reflections of a lost world. Most trilobite fossils, however, are not golden, but instead black or brown. Perhaps because of this, most illustrations of living trilobites show them as black or brown inverted boot prints. This isn’t necessarily sound reasoning, because the color of fossils is largely based on their mineral content. Fossil crustaceans like crabs and lobsters are often black and brown too, but we know from living species that they’re almost never solid black, but come in all manner of colors and patterns.

          Although trilobites are common fossils, they weren’t found in every rock those early “gentleman scientists” looked at. Like all fossils, trilobites are only found in sedimentary rocks, but it’s more specific than that. Trilobites were strictly marine and lived only in the Paleozoic Era, 541-252 million years ago.

Their Extinction

          If we were to travel back in time to the seas of the Paleozoic Era, we’d meet our heroes on familiar reefs and intertidal beaches, where they’d be joined by a largely unfamiliar cast of characters. “Forests” of stemmed starfish relatives called crinoids, lived just below the waves, and the seas were full of shelled relatives of squid and octopi. The reefs themselves were built by encrusting algae and completely extinct types of coral.

          And on those reefs were hundreds of diverse species of trilobites; crawling, digging, swimming; eating, hiding, raising young; living and dying. Earth of the distant past wasn’t inhabited by aliens doing alien things, but by normal animals doing wonderful things.

          Through the nearly 300 million years of the Paleozoic Era, trilobites were hit by multiple mass extinctions, and in one case they were almost wiped out with only one genus making it through. They finally fell victim to extinction 252 million years ago at the end of the Permian Period, in a mass extinction commonly called the Great Dying. This extinction is linked to huge volcanoes in Siberia whose eruptions burnt vast coalfields. The CO2 dumped into the atmosphere from the volcanoes, and especially the coal, led to rapid global warming and ocean acidification. This proved too much for the trilobites to survive and they, as well as 90% of marine animal species, disappeared.

References: Special thanks are owed to paleontologist Dave Rudkin of the Royal Ontario Museum in research and preparation of the illustration. Andy Secher, Martin Shugar. “Trilobite Website.” American Museum of Natural History. Accessed 27 May 2018. Cardiff Curator (@CardiffCurator). “U is for Utah, USA. Native Americans in this area used Elrathia trilobites as amulets to protect against disease and injury #TrilobiteTuesday #Alphabet” 27 Feb 2018, 12:15 AM. Tweet. Jane J. Lee. 2013. “Trilobites Found With Mysterious Markings.” National Geographic News. Accessed 10 April 2018. Markus Martin (@trilobitelegs). “Pregnant for nearly 450 million years...A golden Triarthrus eatoni with soft tissue preservation and eggs. Yay for trilobite eggs!” 20 Feb 2018,7:03 AM. Tweet. M. Gabriela Mángano, Luis A. Buatois, Ricardo Astini, Andrew K. Rindsberg. 2014. “Trilobites in early Cambrian tidal flats and the landward expansion of the Cambrian explosion.” Geology; 42 (2): 143–146. Raymond C. Moore. 1959. “Treatise on Invertebrate Paleontology Part O, Arthropoda 1.” Geological Society of America, University of Kansas Press. Richard Fortey. 2001. “Trilobite: Eyewitness to Evolution.” Vintage. Richard Fortey. 2004. “The Lifestyles of the Trilobites.” American Scientist, Volume 92. Sam Gon III. “A Guide to the Orders of Trilobites.” Accessed 27 May 2018.

The Confusing term "ONYX"

What does it mean and why can it look so different?

Onyx is a term that is hard to pin down. Onyx can mean different things to different people. It has become a generic term for a number of banded minerals that have become popularly known as Onyx, but they can be banded calcite. At the same time, the term Onyx' means a specific thing, referring to a black chalcedony that can have white bands running through it. So Onyx is a specific mineral chalcedony (micro-crystalline Quartz) and a trade name for banded Calcite and sometimes other banded stone materials as well.

From Wikipedia:

Onyx primarily refers to the parallel banded variety of chalcedony, a silicate mineral (Quartz)Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands: agate has curved bands and onyx has parallel bands. The colors of its bands range from black to almost every color. Commonly, specimens of onyx contain bands of black and/or white. Onyx, as a descriptive term, has also been applied to parallel banded varieties of alabaster, marble, calcite, obsidian and opal, and misleadingly to materials with contorted banding, such as "Cave Onyx" and "Mexican Onyx".

So what does that mean?

As stated, onyx is both a banded chalcedony of very good to excellent quality for carving and jewelry that is a quartz mineral. Or it is a colored banded calcite or banded stone visually related to banded calcite. There are even websites that will argue that there are additional differences between Banded Agate (chalcedony) and true Onyx. So how do you tell? Well, that's why we're here today!

Round Onyx Cabochons

Back and white Onyx cabochons, some with translucent banding.

Oval Sardonyx Cabochons

Red-Orange and white banded Carnelian (Sardonyx) cabochons.

To Onyx, or not to Onyx... That is the Question!

In many ways, probably 90% of the time, it's really easy to tell if you're getting Onyx or something that is just traded under the name of Onyx. If it's a deep black color or banded blacks and white, mostly opaque, and has a polished shiny glass-like or vitreous luster, it's probably Onyx. Onyx like this is usually carved and polished to be cabochons for wearing in jewelry.

If it's rusty red or orangy-red and white banded material and is hard and shiny like glass, it's probably what we call "Sardonyx" or "sard" or even "Red Onyx".This is the same thing as Onyx (banded chalcedony or Quartz) but is red-orangy in color with white bands. They might also call this Carnelian; which is really the same thing; we're just splitting hairs. Please note the examples.

If it's not the above, and instead has a waxy luster and seems like you might be able to scratch it with your fingernails, its colorful with different bands running through it, and it's NOT black, you probably have banded calcite that's being called Onyx under the trade name. The hardness for calcite is around 3, and your fingernail (untreated) is about 2.5, so it kind of feels like you can scratch or mar it a bit just by running your fingernail along it.

Chalcedony and Quartz have a hardness of 6.5 to 7, so they will feel glassy hard and not as easy to scratch. It also takes a polish better than calcites and alabaster and many other materials sold under the trade name of "Onyx". The material very often looks shinier and smoother, but not always.

Examples of Polished Stones called Onyx

Banded Calcite, Marble, and Alabaster Examples

If it's not black and white and seems banded with many colorful layers, and feels a bit soft in your hand, it's probably calcite. There are many places in the world where calcite is mined and distributed under the trade name of "Onyx". Places like Iran, Mexico, Arizona, Morroco, all over. In addition to banded calcite being sold as "Onyx", there is also marble, alabaster, and other banded translucent stone sold under the same "Onyx" trade name. Onyx is really just a generic term that does not have any real meaning anymore other than it's popularly known. Here are a few examples that you can visually scan. Some are Mexican calcite, some are Alabaster, some are marble or cultured granite, and yet they are all sold as Onyx!

We would forewarn you that countertop places love to just call things what they want, just like paint colors have all kinds of crazy names, so make sure that when you're looking for countertops, it's not calcite. It's pretty but too soft for everyday living.

The Acid Test

Lastly, if you really gotta know, sometimes a bit of white vinegar can do the trick. The acid in the vinegar will eat at the calcite, and it will bubble or foam a bit, but only do that with permission and in a place that doesn't show. Vinegar will not harm Quartz or Chalcedony.

The Above Example: Swatches of banded calcite, alabaster, marble, granite, and many cultured stone products are sold under the name of "Onyx". Can you tell which is which? Well, none of them are actually the Quartz variety of true onyx.

Pink & Rose QUARTZ

Can you tell the difference just by looking at it?

All Credit to Steve Voynick of Rock and Gem Magazine (Feb. 2023) for this Article

Rose quartz ranks high among the most attractive and familiar of the many color varieties of quartz. Its delicate pink color, soft translucency, and affordability make it a popular gemstone. Pink quartz is a much lesser-known variety of quartz. While similar to rose quartz in color, it differs markedly in structure, degree of transparency, the origin of color, occurrence, rarity, and cost.

Pink QUARTZ

Pink quartz, a pink macrocrystalline variety of quartz, was discovered in pegmatites at Rumford, Maine, and first described in mineralogical journals in 1938. But these specimens attracted little attention from mineralogists or collectors at the time. Initially, they were assumed to be a rare, atypical subvariety of rose quartz.

 

Then in 1959, pegmatite miners in Brazil’s gemstone-rich Minas Gerais state discovered clusters of beautifully developed, terminated, hexagonal quartz prisms. These crystals had water-clear transparency and a pink color that was similar, but not identical to, the color of rose quartz. When these specimens appeared on the collector markets of Europe and the United States, the limited supply was snapped up by both collectors and mineralogists.

Mineralogists soon learned that the color of pink quartz, unlike that of rose quartz, is created when some silicon ions within the quartz crystal lattice are replaced by trivalent aluminum ions and pentavalent phosphorus ions. This partial replacement renders the lattice susceptible to distortion from the energy of natural geophysical radiation, creating color centers that form when radiation displaces phosphorus ions from their normal lattice positions, leaving voids that trap electrons. When white light boosts these trapped electrons to higher energy levels, they return to their normal levels by releasing excess energy as visible light that we perceive as pink or pale red.

Pink and Citrine Quartz Crystals

Pink Quartz crystals surround the center of golden Citrine Quartz. Photo credit to Wikimedia Commons.

Pink Quartz from Brazil

Pink Quartz Specimen from Brazil. Photo credit to Psycodelic Rocks/IG

Raw Rose Quartz

Raw Rose Quartz. Image Credit to Cape Code Crystals.

Cut Star Rose Quartz

Rose QUARTZ

Rose quartz always occurs in massive form without crystal faces or terminations. It is almost always translucent, with a uniform color distribution, and is found mainly in the core zones of granite pegmatites.

Mineralogists had traditionally attributed the color of rose quartz to traces of titanium and, to a lesser extent, iron and manganese. These impurities were thought to distort the crystal lattice, causing it to reflect and transmit red wavelengths of light which the human eye perceives as varying shades of pink.

More recent studies have shown the pink color is because of fibrous inclusions. After dissolving rose quartz from several different sources in hydrofluoric acid, researchers have recovered residues of flaky, pink-colored nanofibers, most consisting of dumortierite and other aluminum borosilicates.

Although these nanofibers make up only about one-tenth of one percent of the overall weight of rose quartz, they are highly reflective and create both its characteristic pink color and its soft translucency. Usually aligned along the axes of quartz’s hexagonal crystals, these inclusions also explain the six-rayed asterism that appears in the star variety of rose quartz.

Star Rose quartz cut spheres showing the asterism of fibrous inclusions along the hexagonal axis. Photo credit to Martin P. Steinbach. 

The differences

The inclusions in massive rose quartz inhibit crystal development, while the absence of inclusions in pink quartz ensures normal crystal development and a high degree of transparency. In addition, the color of pink quartz is often zoned and most intense near the crystal terminations. The color of crystalline pink quartz also fades slowly with prolonged exposure to sunlight, while the color of massive rose quartz is stable. And pink quartz is sometimes intermixed with citrine, the golden-yellow color variety of quartz.

The formation of pink quartz requires unusual and complex chemical and physical conditions that include partial ionic replacement within the quartz lattice, sufficient geophysical radiation to create color centers and enough space to permit crystal growth. Because these conditions don’t often occur together, pink quartz, unlike rose quartz, is rare, costly and found in only a few localities. A fine specimen of pink quartz can cost hundreds of dollars.

Another difference between the rose and pink subvarieties is size. Rose quartz often occurs in large masses; pink quartz is found only as crystals an inch or two in size. Given these collective differences, the term pink quartz is now used to differentiate crystalline pink quartz from massive rose quartz.

 

In general usage, the descriptive color terms pink and rose are often imprecise. Rose quartz is sometimes sold as pink quartz and vice versa. Also, massive rose quartz is frequently cut into hexagonal prisms for use in pendants; while these may appear to be natural crystals of pink quartz, their translucency immediately identifies them as rose quartz. Pink quartz is almost always retained as a specimen in its natural form.

Scorodite

This Mineral is all about the Blues

Named for the Greek scorodion, meaning “garlic,” in reference to the garlicky smell Scoodite produces when heated.  From hundreds of occurrences, usually in small amounts, including Germany, the Czech Republic, Austria, England, Algeria, particularly large crystals from Namibia, Brazil, Mexico, the USA, Japan, and Australia. Scorodite forms as a secondary mineral from the oxidation of arsenic-rich sulfides. Scorodite is an oxide mineral of iron and arsenic with the composition FeAsO4•2H2O. Scorodite weathers to limonite. Scorodite was discovered in the Schwarzenberg, Saxony district, ErzgebirgeSaxonyGermany. Scorodite follows the orthorhombic crystal structure and has a Mol's hardness of 3.5 to 4.

Scorodite can be a beautiful crystal can be easily confused with euclase and even tanzanite and celestine. Its crystals can appear similar to all these, and its color can mimic these minerals as well. Transparent and clean crystals of scorodite demand a strong price from collectors and can fetch prices higher than many of the minerals it appears like.

Why is scorodite about the blues, you might be asking? Well, for its obvious blue coloration and its ability to easily fool a rock hunter into thinking he has found copper, sapphires, blue euclase, or even an out-of-place tanzanite vein. But its beautiful azure crystals can still fetch a fine price!

Scorodite Resembling Euclase

Unique Scorodite from Namibia. Credit: Key Minerals

Scorodite Resembling Blue Apatite

Locality: Hezhou Prefecture, Guangxi Zhuang Autonomous Region, China

Scorodite Resembling Tanzanite

Scorodite, Namibia.

Scorodite Resembling Celestite

Scorodite from Ojuela mine, Mapimi, Durango, Mexico

Scorodite Resembling Euclase

Scorodite. Tsumeb Mine, Tsumeb, Oshikoto Region, Namibia. Credit: Heritage Auctions

CUPRITE

A Beautiful and Geometric Copper Mineral

Stunning Cuprite from Villecun, Olmet-et-Villecun, Hérault, Occitanie, France

Stunning Cuprite Crystals. Photo by: Laurent Kbaier

Red Dome Mine, Chillagoe, Queensland, Australia by Joe Budd

Cuprite is named for the Latin cuprum, "copper," in allusion to its copper content. Its chemical formula is Cu2O. It can form as bright transparent red crystals or as lustrous, submetallic opaque crystals. Even the opaque form will have slightly red edges and faint transparency upon back-lighting. Cuprite is often associated together with Native Copper in copper deposits and frequently forms as an encrusting reddish coating over the Copper. Malachite is known to fully or partially coat a layer or pseudomorph over Cuprite, forming an interestingly shaped and sometimes sparkling green crystal form.

Cuprite usually forms in octahedral crystals or in groups of octahedral crystals, sometimes with modified cubic crystal edges. it forms less commonly in cubic or in cubic clusters. Rarely in dodecahedral or modified dodecahedral forms and sometimes twinned as penetration twins, and occasionally in hopper growths.

Cuprite is commonly found as an oxidation product of copper sulfides in the upper zones of veins, often associated with Native CopperMalachiteAzuriteLimonite, and Chalcocite. A fibrous form of Cuprite is known as Chalcotrichite. In rare or perfect conditions, it forms beautiful transparent bright red gem-quality crystals, but most of the time, the crystals are opaque or nearly opaque. In spite of its nice color, it is rarely used for jewelry because of its low Mohs hardness of 3.5 to 4. Faceted cuprite of any size is considered one of the most collectible and spectacular gems in existence, with its deep garnet coloring and higher brilliance than a diamond. Only the gem's soft nature prevents it from being among the most valuable jewelry stones.

Trilliant Cut Cuprite

For the December story, we're featuring two minerals in a head-to-head shoot-out of chemistry and qualities. These two are very similar, in name, chemistry and how they can look, but they are distinctly different minerals.

So what's it gonna be? 

Bornite vs Bournonite
While these two minerals share a similar locations and they are from the sulfides mega-group of minerals. Both these have a metallic luster, contain copper and can have bluish tarnish. Here is how they break down.

Bornite

Formula: Cu5FeS4 - A Copper Ferric Sulfide

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  • An important Copper ore

  • Fresh surfaces can tarnish to various iridescent shades of blues to purples.

  • It is named after Hungarian Mineralogist Ignaz Von Born.

  • Comes in around 3 to 3.25 on the Mols hardness scale.

  • Often called Peacock Ore, Sometimes called Bornite.

  • Its color is caused by oxygen tarnishing.

Bournonite

Formula: PbCuSbS3 - Lead Copper Antimony Sulfosalt

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  • An important metal ore.

  • A steely grey color with a metallic luster that sometimes tarnishes.

  • Named in 1805 in honor of Jacques-Louis, Comte de Bournon.

  • Comes in around 2.5 to 3 on the Mols hardness scale.

  • Often confused with, and found with other sulfosalts.

  • Its color can be caused by oxygen tarnishing.

Bornite, also known as peacock ore, is a sulfide mineral with chemical composition Cu5FeS4 that crystallizes in the orthorhombic system (pseudo-cubic). It occurs globally in copper ores with notable crystal localities in ButteMontana and at BristolConnecticut in the U.S. It is also collected from the Carn Brea mine, Illogan, and elsewhere in CornwallEngland. Large crystals are found from the Frossnitz Alps, eastern TirolAustria; the Mangula mine, Lomagundi districtZimbabwe; from the N'ouva mine, TalateMorocco, the West Coast of Tasmania and in DzhezkazganKazakhstan. There are also traces of it found amongst the hematite in the Pilbara region of Western Australia.

Bournonite is a sulfosalt mineral species, trithioantimoniate of lead and copper with the formula PbCuSbS3. The crystals are orthorhombic, and are generally tabular in habit owing to the predominance of the basal pinacoid; numerous smooth bright faces are often developed on the edges and corners of the crystals. They are usually twinned, the twin-plane being a face of the prism (m); the angle between the faces of this prism being nearly a right angle (86° 20′), the twinning gives rise to cruciform groups and when it is often repeated the group has the appearance of a cog wheel, hence the name Rãdelerz (wheel-ore) of the Kapnik miners. The repeated twinning gives rise to twin-lamellae, which may be detected on the fractured surfaces, even of the massive material.

Montana Bornite

Bornite from Montana, USA. (public display, Montana Bureau of Mines and Geology Mineral Museum, Butte, Montana, USA)

Bournonite on Quartz

Bournonite on Quartz: Yaogangxian Mine, Yizhang County, Chenzhou Prefecture, Hunan Province, China

Lazaraskeite

A First Discovered Mineral that is Organic, Carbonate and Glycolate

Congratulations to University of Arizona Geoscientist Dr. Hexiong Yang and his colleagues for the discovery of a new mineral named Lazaraskeite, which has been published in the latest issue of “American Mineralogist, Vol 107, p 509-516, 2022”. Lazaraskeite represents the first organic mineral that contains glycolate. Its discovery implies that more glycolate minerals may be found and suggests that glycolate minerals may serve as a potential storage for biologically fixed carbon. It was found in the Western end of Pusch Ridge in the Santa Catalina Mountains, north of Tucson, Pima County, Arizona, USA. In order to be declared a new mineral, it has to be a naturally occurring crystalline substance, so man-made or industrial versions of the copper-glycolate substance don't count.

It resembles pale cyan blue to blue prismatic or bladed crystals, which many copper compounds exhibit, like veszelyite, clinoclase, and chalcanthite. The identification of this mineral is confirmed by single-crystal X-ray diffraction and chemical analysis.

Named in honor of Warren Lazar, an American prospector who discovered the mineral, and his wife Beverly Raskin Ross. They provided the first specimens for study. It has a chemical formula of Cu(C2H3O3)2. As any organic compound, the formula may also be written as Cu(OCOCH2OH)2 or Cu[O(CO)CH2(OH)]2. Associated minerals include chrysocolla, malachite, wulfenite, mimetite, hydroxylpyromorphite, hematite, microcline, muscovite, and quartz. Both polytypes are greenish-blue in transmitted light, transparent with a white streak, and have a vitreous luster. This crystal is brittle, has a Mohs hardness of ~2, and follows the monoclinic system.

Sources: https://pubs.geoscienceworld.org/msa/ammin/article-abstract/107/3/509/612025/Lazaraskeite-Cu-C2H3O3-2-the-first-organic-mineral, https://www.mindat.org/min-53400.html, https://www.geo.arizona.edu/news/2022/04/lazaraskeite-brand-new-mineral-first-organic-mineral-contains-glycolate-discovered-our, https://rruff.info/lazaraskeite/R180026

Lazaraskeite from Arizona
Lazaraskeite Ruff Database
Lazaraskeite (copper glycolate) from Arizona

For the September story, we're featuring two minerals in a head-to-head shoot-out of chemistry and qualities. These two have caused a fair amount of confusion over the years as they can be visually very difficult to tell apart. They are both often used in jewelry making and carved into cabochons.

So what's it gonna be? 

Variscite vs Turquoise
While these two minerals share a similar color but they are from the same phosphates mega-group of minerals. Both these sought-after gemstones are members of the Aluminum Phosphates group and both are greenish to blue-green in coloration. Here is how they break down.

Veriscite

Formula: AlPO4 · 2(H2O)

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  • A rare to find hydrated Aluminum Phosphate.

  • Found in Aluminum rich rocks near the surface.

  • A vivid greenish to other colored phosphate.

  • It is named for the German location it was first discovered.

  • Comes in at 3.5 to 4.5 on the Mols hardness scale.

  • Sometimes called Verdite, Veriquiose, or Utahite.

  • The green color is from chromium impurities.

Variscite is a secondary mineral formed by direct deposition from phosphate-bearing water that has reacted with aluminum-rich rocks in a near-surface environment. It occurs as fine-grained masses in nodules, cavity fillings, and crusts. Variscite often contains white veins of the calcium aluminum phosphate mineral crandallite.

It was first described in 1837 and named for the locality of Variscia, the historical name of the Vogtland, in Germany. At one time, variscite was called Utahlite. At times, materials that may be turquoise or may be variscite have been marketed as "variquoise". Appreciation of the color ranges typically found in variscite have made it a popular gem in recent years. Varisite can have quite a bit of color variability from blue-green to pale green with veining remarkably similar to southwestern turquoise.

Variscite cut slab from Fairfeild, Utah USA

Variscite slab from Fairfield, Utah measuring 20cm.

Variscite Cabochon

Variscite cabochon from Gem Select.

Turquoise

Formula: CuAl6(PO4)4(OH)· 4(H2O)

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  • A rare to find hydrated Copper Aluminum Phosphate.

  • Found in Copper-rich regions.

  • Named from the Turkish region that it was brought to Europe originally.

  • Comes in at 5 to 6 on the Mols hardness scale.

  • It is known by many names from all over the world.

  • The green color is from chromium impurities.

Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminum. It is rare and valuable in finer grades and has been prized as a gemstone and ornamental stone for thousands of years owing to its unique hue. Like most other opaque gems, turquoise has been devalued by the introduction of treatments, imitations, and synthetics into the market. The robin’s egg blue or sky-blue color of the Persian turquoise mined near the modern city of Nishapur in Iran has been used as a guiding reference for evaluating turquoise quality. The color of turquoise and the veining can drastically affect its value.

The gemstone has been known by many names. Pliny the Elder referred to the mineral as Callais (from Ancient Greek κάλαϊς) and the Aztecs knew it as chalchihuitl.

Tourquoise Slabs
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Turquoise slabs cut from the original nodules and Turquoise 
cabochons.

What Makes a Mineral vs. a Gemstone vs. a Crystal

After Many months of writing about minerals and crystals and gemstones, it was brought to our attention that perhaps not everyone may be in the know about why makes a differnce in these terms. They are not interchangeable and they do have specific meanings that distinguish them from each other. Sometimes the distinction can be important, especially if you're thinking about buying a gemstone, there are some question that are good to ask. 

What is a Mineral?

The definition of a minerals contains a list of criteria that firmly define what a mineral can be, and what it not. See the example animations.

  • It occurs naturally - It can be found in nature and is not a man-made substance.

  • It cannot contain organic molecules.

  • It is a solid in its environment, because of the next statement.

  • It has an ordered atomic or chemical structure that repeats itself in a predictable pattern. In other words, the atoms that make it up can be predicted in name and spacial configuration.

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Section of a Mineral Molecule

What is a Crystal?

The definition of a crystal contains a list of criteria that firmly define what a crystal is, and its definition includes more options than a mineral. Its criteria is a bit wider.

  • It occurs naturally or can be a man made substance. Synthetically created diamonds and rubies mimic a natural mineral, but because they are man-made they cannot be classified as a mineral.

  • It is a solid in its environment.

  • It can be inorganic, or organic in chemistry.

  • It has an ordered chemical structure that repeats itself in a predictable pattern.

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Section of DNA Molecule

What is a Gemstone?

The definition of a gemstone takes a different tact. It loosely describes what a gemstone should be, but to be honest, a gemstone can be many things that provide focus to a piece of jewelry.

  • Can be a precious or semi-precious stone. (A stone is non-metallic earth or mineral matter hardened together in a mass.)

  • A gemstone does not need to be a mineral or a crystal. Opals and amber are considered gemstones, but they don't meet the strict definition of either state. Even glass and coral or an ammonite fossil can be a gemstone, but its not a crystal or mineral.

  • Being rare, beautiful to the beholder, and a fairly hard substance can definately help with longevity of a jewelry piece, and are all good qualifications, but not required.

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Ammonite (Fossil-Opalized) Gemstone

Some Additional Context: In the three definitions, each one is unique. Its good to remember that these terms are often used incorrectly and sometimes interchangeably. By definition, a mineral has to be a crystal, but a crystal can be things that a mineral is not. Frozen water (ice) is a mineral, but sugar is a crystal since it contains organic chemistry. Fossils and opals can be considered gemstones, but they are not minerals, Crystalline substances like synthetic emerald can be a gemstones and a crystal, but are held to a different standard than naturally found gemstones. Even glass can be considered a gemstone, but it's not a mineral or a crystal, it merely serves as the focus of a jewelry piece. If your buying from someone you are not familiar with, best to ask what it is, and possibly what it is not, before you buy.

For the July story, we're featuring two minerals in a head-to-head shoot-out of chemistry and qualities. These two have caused a fair amount of consternation among mineralogists and collectors alike. They are, in a way, the same thing, but how the impurities within the mineral's structure organize themselves, makes all the difference.

So what's it gonna be? 

Gem Silica vs Chrysocolla
While these two minerals share the same color but they are from the same silicates mega-group of minerals. Here is how they break down. They are so similar that some people don't even think that they are different at all, but its the hardness and gem quality that sets them apart.

Gem Silica

Formula: SiO2 Chalcedony with Chrysocolla inclusions

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  • Very rare to find and is always found with copper deposits.

  • A vivid blue-green to turquoise colored variety of Chalcedony.

  • It is named for Silica Quartz family name.

  • Comes in around 6.5 to 7 on the Mols hardness scale.

  • Sometimes called Gem Chrysocolla, Chrysocolla Silica and Chrysocolla Chalcedony.

  • It is a Chalcedony colored by the same copper salts in the mineral Chrysocolla.

Gem Silica is a Chalcedony Quartz. Chalcedony is a form of Micro-crystalline Quartz (the crystals are so small that you can't see them with the human eye). This is why Gem Silica has a hardness around 7, since it is quartz with small amounts of Chrysocolla impurities that are spread within the Chalcedony. The Chrysocolla gives the silica its beautiful and vivid blue-green coloration.

Because Gem Silica is extremely rare to find, and it's a collector's gemstone, prices can be very high depending on its color and translucency–up to $200 dollars per carat. Because of this, there are many fakes on the market like common clear or milky chalcedony that is died to look like gem silica, or even lessor expensive Chrysoprase (Chalcedony colored by Nickel impurities), can be sold under the Gem Silica name. So buyer beware!

gem-silica-chalcedony
Gem-Silica-cabochon

Natural Botryoidal Gem Silica: photo credit to the Arkenstone

Gem Silica Cabochon: Inspiration Mine, Gila County, Arizona.

Chrysocolla

Formula: Cu2-xAlx(H2-xSi2O5)(OH4)•nH2O

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  • A minerals that is always associated with secondary copper minerals.

  • A form of copper salt.

  • It is named for the greek words for gold-glue.

  • Comes in around 2.5 to 3.5 on the Mols hardness scale.

  • A member of the phyllosilicates group.

  • Chrysocolla is colored by the copper salts in the mineral.

  • It is blue to blue green in coloration, but is can be found in other colors.

Chrysocolla is a copper salt phyllosilicate (Silicate rings) with water in its structure. It might seem odd to have water in a mineral, but many minerals do have water as part of their chemistry. It is always found with other copper bearing minerals and around copper mines too. 

It was names by the greek Theophrastus in 315 B.C. and comes from the Greek "chrysos", meaning "gold," and "kolla", meaning "glue," in allusion to the name of the material used to solder gold. André-Jean-François-Marie Brochant de Villiers revived the name in 1808.

It is a relatively soft and easily broken structure. It is typically found as glassy botryoidal or rounded masses or bubbly crusts, and as jackstraw mats of tiny acicular crystals or tufts of fibrous crystals. There are no known large crystals of Chrysocolla. The Chrysocolla "crystals" are all pseudomorphs.

Chrysocolla-Tyrolite-Clinotyrolite

Chrysocolla Formation: Powder-blue chrysocolla as stalactitic growths and as a thin carpet in vugs inside a boulder of nearly solid tyrolite from the San Simon Mine, Iquique Province, Chile (size: 14.1 x 8.0 x 7.8 cm)

Chrysocolla can often be covered and mixed in with Quartz crystals, Chalcedony and Calcite crystals making it very difficult to tell from real Gem Silica. The only way to know for sure is to have the specimen analyzed or looked at by an expert.

Spessartine Garnet

Manganese Aluminum Silicate (Mn3Al2Si3O12)

Spessartine is member of the Garnet group, and is known for its aesthetic orange and reddish-orange colors. This form of Garnet was once much rarer, but new abundant finds in Tanzania, China, and Pakistan have really put Spessartine on the map, making it very well regarded. Spessartine forms a solid solution series with Almandine, and can be virtually indistinguishable from it in localities where both these Garnets occur together. Re-named in 1832 by François Sulpice Beudant after its type locality in the Spessart Mountains, Germany. Previously distinguished as a "manganesian" garnet by Henry Seybert in 1823 using mineral from Haddam, Connecticut, USA. Originally, this mineral, from Spessart Mountains, was called "granatförmiges Braunsteinerz" in 1797 by Martin Klaproth.

A new outstanding occurrence of bright orange Spessartine crystals in Tanzania was first brought to the market in 2008. The deposit is in Nani, Loliondo, Arusha Region, near the Serengeti National Park. Bright orange crystals once came from Marienfluss, Kunene Region, Namibia, but these high quality Spessartine forms are very hard to come across today. Another important African locality is the Jos Plateu, Nigeria. Malaya Garnet (a trade name for Garnet intermediary between Spessartine and Pyrope) is well-known from Mwakaijembe in the Umba River Valley, Tanzania.

Another recent outstanding discovery of Spessartine was in China, where it first discovered in the late 1990's in Tongbei and Yunling, Zhangzhou Prefecture. The Chinese Spessartine is often in dense aggregates of small gemmy crystals coating Smoky Quartz. The finest dark red Spessartine, usually associated with contrasting white Albite, comes from Pakistan at Shengus and the Shigar Valley, Skardu District; and in the Gilgit District. Spessartine of similar quality is also found in Darra-i-Pech, Nangarhar Province, Afghanistan.

Lustrous Spessartine, sometimes in complex crystals with deep etchings, comes from several of the gem pegmatite in Minas Gerais, Brazil, especially at Conselheiro Pena, São José da Safira, and Galiléia, all in the Doce valley. Especially noted is the Navegadora Mine in São José da Safira which produces heavily etched contorted crystals. Other worldwide Spessartine occurrences include Broken Hill, New South Wales, Australia; Val Codera, Sondrio, Italy; San Piero in Campo, Elba Island, Italy; and Iveland, Aust-Agder, Norway.

In the U.S., the most well-known occurrences of Spessartine are the Little Three Mine, Ramona, San Diego Co., California; the Pack Rat Mine, Jacumba, San Diego Co., California; Ruby Mountain, Nathrop, Chaffee Co., Colorado; East Grants Ridge, Cibola Co., New Mexico; and the Thomas Range, Juab Co., Utah.

Sources: Mindat.org, geology.com, minerals.com

Fujian Province Spessartine Garnets

Example of Spessartine Garnets from the Fujian Province, China.

Spessertine-Almandine-Pyrope Garnets

Triangle Chemical Chart of the Pyralsprites garnet group that features Spessartine-Pyrope and Almandine garnet families.

Spessartite Garnets with Cut Gemstones

Several natural uncut Spessartine garnets with cut gemstones made from the same group of crystals. Spessartine gemstones are most prized for their neon-orange to orange-red colors

Spessartine Garnet Close-Up

Example of Spessartine Garnets on matrix as originally found after cleaning. Garnets are known for often form geometric crystals like decahedrons & isocahedron-like shapes.

Spessartine and Smokey Quartz

Example of Spessartine Garnets on that have formed over Smokey Quartz in China.

What Makes Minerals Fluorescent?

Reprinted from Rock & Gem Digital Posting with additions. Original story by Bob Jones.

Fluorite, Scapolite, Willemite with Calcite and Franklinite

The short answer is that some minerals are self-activators. Others depend on some form of impurity that acts as an activator. Minerals that are fluorescent under ultraviolet light are beautiful and fun, however, the great majority of minerals do not respond with color under ultraviolet light. Estimates vary from 10 to 15 percent of the known 5,000 minerals may respond. Including the rare earth elements, there are over 30 different common elements and ions that can cause fluorescence.

Self-Activating Minerals

Self-activating minerals use their own electrons to absorb ultraviolet energy giving their electrons the energy to shift away from the atom’s nucleus to the next higher energy level, or orbital. The remaining light energy is out of balance and reemitted and can be seen as a visible color. Ultraviolet energy is not visible so what you see is the lower electromagnetic energy level resulting from the action of the activator.

What Makes Minerals Fluorescent - Activators

The great majority of activators are atoms of certain metal elements which become part of the mineral’s chemistry by taking the place of atoms in the host mineral. For example, sodium chloride halite normally lacks color but if trace manganese atoms are present, they make the halite glow a lovely red under short wave ultraviolet radiation. When the electrons in a responding mineral shift to a higher orbit they can’t stay there indefinitely. They are constantly shifting with blinding speed between their normal position and a higher orbital as the ultraviolet energy continues. Even though the electrons are shifting, the color we see is steady.

The Process
Fluorescent minerals contain certain atoms with electrons that are taken up to a higher excited energy levels by absorbing energy from the incoming ultraviolet light. These electrons instantly fall back to their original energy levels, giving off energy in form of visible emitted light. This takes place in a very small fraction of a second. We see only the resultant visible light emitted as long as the atoms are exposed to the ultraviolet light. Depending on the energy released when electron returning to their original level, minerals exhibit different fluorescence colors.

Known Activators

As we gain greater ability to pick apart a mineral, we are finding more activators at work and they are not all metal elements. Some are more complex ions. Activators like uranyl oxide are regular participants in many radioactive minerals even with the trace manganese. These common activators have joined with some odd elements you would not think could trigger a color such as lead (Pb) in hydrozincite and sulfur (S) in sodalite, a variety of hackmanite from Canada.

What Makes Minerals Fluorescent - Rare Earth Elements

Rare earth elements are common activators. You see these elements listed at the bottom of the Periodic Table because they share many of the same chemical, physical, and mineralogical properties and a similar electron configuration of two valence electrons in an outer orbital. Since rare earths often occur together in the same deposit, it is inevitable when an activator is present it can be any one of a suite of rare earths rather than just one element.

Two or more rare earth elements have been identified as causing fluorescence in some fluorite, strontianite, calcite, esperite, fluorapatite, powellite and scheelite. These last two are self-activating most often but can also respond to rare earths. The tungstate ion in scheelite is what responds to ultraviolet excitation, usually a brilliant blue under shortwave. In powellite, it is the manganese oxide ion that is the main activator causing a yellow response.

Why Activators Work

There is one other factor worth considering with activators. Why does an activator function only in certain minerals and not in all minerals? There are two reasons. The activator has to have a proper valence or number of electrons in its outer orbital, very often two. Its atoms also have to be close in size to the host atom that it replaces so it becomes part of the mineral’s chemistry and fits in the mineral’s lattice structure.

Manganese

Manganese is the most common activator. It is found in many of the minerals from the Franklin and Sterling Hill mining district in New Jersey causing the town of Franklin to be named the Fluorescent Mineral Capital of the World. Manganese is a transition metal element which means its outer orbital can hold a varying number of electrons, in this case, two-three or four. They can be shared and become the agent in chemical bonding.

Usually, it is manganese valence two that ends up as a trace metal serving as an activator. In the mineral calcite, for example, it has a valence of two and can replace some calcium atoms with a similar valence in the mineral’s lattice structure. Franklin-Sterling Hill calcite depends on manganese as its activator. The calcite can respond as a brilliant red. Studies have shown the optimum content of manganese activator in calcite at Franklin for a strong fluorescent response is about three percent. Too much of a good thing and the response is diminished, or not there at all.

The same valence two of manganese is also responsible for other fluorescent minerals from the Franklin mine. This is because these are zinc minerals and zinc has a valence of two.

 

Size Matters

How about the size of atoms? Zinc atoms are close enough in size to manganese that they can replace some zinc. Willemite easily accepts manganese atoms as an activator resulting in a bright fluorescent response but in this case green, not red.

What Makes Minerals Fluorescent - Other Activators

Other activators are not simple elements. Some minerals may contain a trace of organic material like natural oil and will fluoresce. I recall collecting fluorite that included organics in the quarry at Clay Center, Ohio. The pale brown transparent fluorite cubes had a creamy or slightly bluish color depending on the type of ultraviolet lamp used. Doubly terminated quartz crystals found in Herkimer, New York, may show fluorescence. “Herkimer Diamonds” developed in cavities created by organic stromatolites which existed millions of years ago. They died and left behind organic material which is picked up by the quartz as it forms. That’s what causes the fluorescence.

Recently Discovered Activators

We now know there is another group of activators not known decades ago consisting of two or three different elemental ions. Such things as carbon trioxide (CO3 ) in calcite or topaz may cause a response. Much more important in topaz is the activator titanium oxide ion (TiO6). California’s official gemstone is benitoite a titanium mineral. It fluoresces blue in short wave thanks to the titanium oxide ion (TiO3). Certainly, the most frequently seen ion as an activator is uranyl ion (UO2). It shows up in a host of radioactive minerals as well as other species.

(Back, Left to right) Fluorite, Scapolite, Willemite with Calcite and Franklinite (Front, Left to right) Willemite with Franklinite, Calcite, Opal var. Hyalite

Dugway Geode - normal and UV light

Fluorescent Dugway Geode: Many Dugway geodes contain fluorescent minerals and produce a spectacular display under UV light! Specimen and photos by SpiritRock Shop.

4-colored, fluorescent specimen is from the famous Franklin Mine

This spectacular, 4-colored, fluorescent specimen is from the famous Franklin Mine, Franklin, Sussex County, New Jersey. Minerals are Clinohedrite, Hardystonite, Willemite, and Calcite. 

Quenchers

While it seems that all radioactive minerals should fluoresce, they do not. Uraninite, the main uranium oxide mineral does not respond at all. A host of the popular radioactive minerals, like autunite, do fluoresce. But, the copper uranium mineral torbernite may not. This brings up the idea of quenchers, trace minerals that inhibit or prevent a fluorescent response.

Copper promotes good color in many minerals like azurite and malachite. If copper is present in non-copper species that might otherwise fluoresce, they will not. Copper quenches the fluorescence, but not always. Normally, adamite is just about colorless but a little copper gives it that rich lime green color. Mexican adamite will fluoresce a bright green color because of the uranyl ion. The fluorescent response varies from brilliant green to no response at all. It all depends on the copper-uranyl relationship controlling the effects of ultraviolet.

Another quencher is iron. But again we find a conundrum. Iron minerals don’t fluoresce. But the iron in trace amounts of a mineral can be an activator as in some feldspars like anorthoclase. It can also be an activator in petalite and pectolite, though they tend to react better with other activators. Iron ions are also responsible for many gemstone's colorations of blues and yellows in teh visible spectrum.