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This Month's Featured Story

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

Previously Featured

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
polished-turquoise.png

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.

Animation_of_Crystal_Structure_of_WurtziteVarTwo.gif

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.

Rectangle-Opal-Photography.gif

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.

Unknown Activators

There are still a great number of minerals that fluoresce because of some unknown activator. A particular mineral species may or may not fluoresce depending on where it is found. This is what makes collecting fluorescent minerals so exciting. Coupled with the wide range of ultraviolet equipment, and the continuing discovery of more mineral species that fluoresce, the hobby will continue to grow.

Sources: https://www.earthsciences.hku.hk/shmuseum/earth_mat_1_2_6.php, https://geology.com/articles/fluorescent-minerals/, https://geology.com/articles/fluorescent-minerals/, https://www.naturesrainbows.com/post/clinohedrite-hardystonite-willemite-and-calcite-franklin-mine-franklin-new-jersey

For the March story, we're featuring two minerals in a head-to-head shoot-out of chemistry and qualities. Once again, these two minerals are named very similarly but are quite different.

So what's it gonna be? 

Rosolite vs Rubellite!
While these two minerals share reddish names but they are from two completely different families within the silicates mega-group of minerals. Here is how they break down.

Rosolite

Formula Ca3Al2(SiO4)3 - Garnet Family

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  • Usually found as Isometric and geometric crystals in small pockets.

  • A light pink to red variety of Grossular Garnet.

  • It is named for its pinkish-red color.

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

  • Sometimes called Raspberry Garnet for its appearance.

  • Garnets are a very diverse group of minerals that share a varied chemical structure with a silicate core.

Rubellite

Formula A(D3)G6(T6O18)(BO3)3X3Z - Tourmalines

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  • Typically found in columnar prismatic crystals in the trigonal crystal habit

  • From the latin word 'rubellus' meaning 'reddish'.

  • Comes in at about 7 on the Mols hardness scale.

  • Large transparent red Rubellite crystals are rare and highly sought after by collectors.

  • The tourmaline family is a large and colorful family of minerals. Rubellite is the pink to red variety of Elbaite Tourmaline and is very rare.

  • Sometime mistaken for Ruby.

Rosolite Grossular Garnet

Rosolite Garnet Crystal from Lake Jaco area in Sierra de la Cruz, Coahuila, Mexico.

Rubelite Tourmaline

Rubellite in matrix from Jonas Mine, Conselheiro Pena, Doce valley, Minas Gerais, Southeast Region, Brazil

For Your Favorite Collector at the Holidays...

Six Rare and Collectable Gemstones & Minerals Ideas

There are probably thousands of rocks and minerals that we could call the rarest and most expensive that have come and gone, but what about the ones that are still somewhat readily collectible? If you want to surprise your favorite collector, here are some of the best rocks and minerals still available in a short list that should give you a great start:

Gem Silica

Chrysocolla is a beautiful blue mineral often mistaken for turquoise. Unfortunately, Chrysocolla in its purest form, is soft and brittle, making it unsuitable for use in jewelry. Occasionally, the same copper salts that give Chrysocolla its wonderful blue color, naturally stain normally colorless chalcedony quartz, giving it a wonderful translucent to transparent blue color. Natural Gem Silica is extremely rare and cabochons made from high-quality Gem Silica can cost more than $100 per carat. Other gemstones made from chalcedony include Chrysoprase and Carnelian. These gemstones, while beautiful, are not nearly so rare and are considerably less expensive. Due to the high demand and high price of quality Gem Silica, care should be taken when purchasing Gem Silica. There are many examples of lower quality non-transparent, Chrysocolla being sold today.

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British ColumbianJade

There are two completely different types of Jade, Nephrite Jade, and Jadeite. British Columbia Green Jade is a type of Nephrite Jade. Jadeite is about the same hardness as quartz. Nephrite Jade is softer than Jadeite, however, it is much tougher (harder to break), making it ideal for carving and use in jewelry as well as non-traditional uses such as interior or exterior tiles. Described as the “toughest natural stone on earth”, Nephrite Jade is extremely hard to mine because traditional mining methods are virtually useless due to the toughness of the material, and using explosives proves damaging to the Jade.

          Extreme high-pressure hydraulic splitters can be used if there are any existing fractures available in the jade however typically, the jade is removed by using huge circular diamond saws or diamond wire saws. Very short summer conditions also prevent British Columbia Jade from being extracted for a few months per year. Although the deposits of Nephrite Jade are quite extensive, the costs associated with extracting the material, along with the short summers and limited production, make it difficult to satisfy the demand for high-quality jade.

Russian Charoite

Russian Charoite is a beautiful lavender to deep purple gemstone with swirls of other colors such as green, black, and sometimes orange. The most notable characteristic of Russian Charoite besides the wonderful color is its chatoyancy or better known as the “cat’s-eye effect”. Russian Charoite was first discovered in the late 1940s although it did not become popular until recent years.

Over the last few years, the price for Russian Charoite has shot up dramatically. Those who were fortunate to invest in Charoite several years ago made a great investment indeed!

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Meteor Rock

Rarer than gold, platinum, or diamonds, meteor rock, or meteorites, commonly known as fallen stars, can sell for many times the price of gold, sometimes selling for more than $300 per gram. These bits and pieces of space debris, survived their fiery descent through the earth’s atmosphere, landing on earth, just waiting to be found by treasure hunters. Each meteorite has its unique size and shape and is usually made up of stone or iron.

The most common meteorites are made of iron and nickel. If they are polished and acid-etched, they will display a wonderful geometric pattern that is highly sought after by collectors.

Victoria Stone

Seldom do man-made stones get classified as gemstones. Victoria Stone is one of those rare exceptions. Created by Dr. Imori beginning in the late 1960s, Victoria Stone was created using a mixture of natural minerals such as quartz, feldspar, calcite, and magnesite.

          These natural minerals were melted and then were made to crystallize using his secret formula, creating a new rock that has wonderful patterns and chatoyancy (cat’s-eye effect). Unfortunately, Dr. Imori died before passing on his secret formula and the process has never been duplicated. As a result, Victoria Stone is quite rare today and commands a hefty price.

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Lander Blue Turquiose

If we’re looking for the rarest and most valuable turquoise in the world, you would be looking for Lander Blue Turquoise. Lander Blue Turquoise was mined in Lander County, Nevada, and was first claimed in 1973. Less than 110 pounds of this fantastic bright blue spider-web turquoise was ever mined.

          If you want to collect some of this rarest of turquoise, expect to pay over $200 per carat and that’s for the small cabochons.

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Happy Hunting!

For the December story, we're featuring two minerals in a head-to-head shoot-out of chemistry and qualities. Once again, these two minerals are named very similarly but are quite different.


Zincite vs Zinkenite!
While these two minerals have a similar name, they are from two completely different families of minerals. Here is how they stack up to each other.

Zincite

Formula ZnO - Oxides Family

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  • Found as translucent hexagonal di-pyramidal crystals in red, orange, yellow, white, and sometimes green coloration.

  • Originally called Red Oxide of  Zinc and Starolite.

  • Comes in around 4 on the Mols hardness scale.

  • Most Zincite crystals are a man-made by-product.

Zincinite

Formula Pb9Sb22S42 - Sulfosalts Family

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  • Typically found in columnar crystals that strongly resemble stibnite. Small clusters of crystals can be needle-like formations.

  • Named after Johann Zinken and contains no Zinc.

  • Comes in at about 3.5 on the Mols hardness scale.

  • Its crystals are often an opaque metallic steely coloration.

Zincite is the mineral form of zinc oxide (ZnO). Its crystal form is rare in nature; a notable exception to this is at the Franklin and Sterling Hill Mines in New Jersey, an area also famed for its many fluorescent minerals. It has a hexagonal crystal structure and a color that depends on the presence of impurities. The zincite found at the Franklin Red coloration is mostly due to iron and manganese, and associated with willemite and franklinite.

Zincite crystals can be grown artificially, and synthetic zincite crystals are available as a by-product of zinc smelting. Synthetic crystals can be colorless or can range in color from dark red, orange, or yellow to light green.

Zinkenite is one of a few sulfide minerals that form fine acicular crystals that appear as hair-like fibers. The fibrous aggregates may be so thick as to cover a specimen with a mat of hair-like fibers or it may be sparsely disseminated between other minerals and may be confused with stray hairs or dark lint. Jamesoniteboulangerite, and millerite are other sulfides that form similar acicular crystals. These sulfides as well as zinkenite have been called "feather ores" because of this unusual habit. Zinkenite is a sulfosalt, a segment of sulfides where the antimony acts more like a metal than a non-metal and occupies a position where it is bonded to sulfurs. A variety of zinkenite from Tasmania contains small amounts of silver.

Man-made Zincite Crystals

Orange-Red Zincite Crystals from a Polish Zinc Smelting Plant.

Zinkenite Crystals

Zinkenite Crystal from the San Jose Mine in Bolivia

Red Beryl

A Gem ‘Rarer Than Diamond and More Valuable Than Gold’

Red Beryl Crystal
Red Beryl Cut Gemstone
Red Beryl

"What Gemstone is found in Utah that is rarer than diamond and more valuable than gold?” That was the compelling headline penned in 2002 by the Utah Geological Survey to introduce its readers to red beryl, a little-known gemstone found primarily in the state’s Wah Wah Mountains.

Discovered in 1904 by Maynard Bixby, this raspberry-red gem had the bookkeeper-turned-miner scratching his head. He had a hunch that the stunning crystals represented a variety of beryl, but the red color didn’t correlate with any beryl known to exist at the time.

Today, the best-known varieties of beryl include emerald (green), aquamarine (blue), morganite (pink), and heliodor (yellow). One year after Bixby’s discovery, W.F. Hillebrand, a geochemist from the National College in Washington, D.C., confirmed that Bixby’s find was a new type of beryl. In 1912, Dr. A. Eppler named the fiery gem “bixbite” in his honor.

The name beryl comes from the Greek word “Beryllos” which means sparkling or brilliant. The well-known varieties of beryl include emerald, aquamarine, and morganite. With Mohs hardness of 7.5-8.0, they are not as hard as topaz, rubies, sapphires or diamonds, but they are all suitably hard for jewelry applications.

Over time, bixbite assumed several names, including “red emerald” and the more proper “red beryl.” The name bixbite fell out of favor because it was often confused with bixbyite, a black manganese iron oxide also discovered by Bixby, in 1897.

Even though more than 100 years have passed since Bixby first encountered the curious red variety of beryl, the mineral has been unearthed in just a few locations — Utah’s Thomas Range, Utah’s Wah Wah Mountains, and New Mexico’s Black Range. The extremely rare variety of the mineral which gets its red color from trace amounts of manganese, red beryl has only been discovered in Utah, New Mexico, and Mexico. Furthermore, the Ruby Violet mine in the Wah Wah Mountains of Utah closed in 2001, is the only source in the world that has provided crystals suitable for cutting. The Utah Geological Survey estimated that one crystal of red beryl is found for every 150,000 gem-quality diamonds. In 2006 the Jewelers Association designated red beryl as the world’s rarest colored gemstone.

Of the three, only the Wah Wah Mountains have produced gem-grade crystals that are large enough to be faceted. The gems are primarily sourced at the Ruby-Violet Claim in Beaver County, Utah. The best specimens of red beryl display a raspberry-pink to slightly purplish-red color.

Writing for the Utah Geological Survey, Carl Ege noted that red beryl was worth 1,000 times more than gold and was so rare that one red beryl crystal is found for every 150,000 diamonds. Because red beryl is rarely found in large sizes, the Gemmological Association of Great Britain estimated that a 2-carat beryl has the same rarity as a 40-carat diamond.

The Briti