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ClassicGems.net |
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Anhydrite |
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Discovered in 1795 (or 1804); IMA status: Valid (pre-IMA; Grandfathered) |
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Chemistry |
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CaSO4 |
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Calcium Sulfate |
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Molecular Weight: |
136.14 gm |
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Composition: |
Calcium |
29.44 % |
Ca |
41.19 % |
CaO |
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Sulfur |
23.55 % |
S |
58.81 % |
SO3 |
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Oxygen |
47.01 % |
O |
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100.00 % |
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100.00 % |
= TOTAL OXIDE |
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Classification |
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Sulfates |
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5/B.04-40 |
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7 : SULFATES (selenates, tellurates, chromates, molybdates,
wolframates) |
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Related to: |
Dehydrated form of Gypsum. Isostructural with Ferruccite. |
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Members of Group: |
n/a |
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Varieties: |
Angelite, Bowel Stone, Vulpinite |
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Synonyms: |
Anhydrous Gypsum, Anhydrous Sulfate of Lime, Calcium Sulfate, Cube Spar, Karstenite, Muriacite, Siliceous Anhydrous Gypsum |
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Crystal Data |
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Crystals tabular on {010}, {100}, or {001} or equant with large pinacoidal faces; elongated along [100] or [001], to 15 cm, with about 40 forms recorded. Typically granular, nodular, parallel or divergent fibrous, massive. Contorted concretionary forms (Bowel Stone). |
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Simple or repeatedly on {011}, common; contact twins rare on {120}. |
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Physical Properties |
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Perfect on {010}, nearly Perfect on {100}, Good to Imperfect on {001}; yielding pseudocubic fragments. |
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Irregular/Uneven, Spintery |
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Brittle |
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3.0 - 3.5 |
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2.96 - 2.98 (g/cm3) |
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Occassionally red under LW UV. Some specimens are fluorescent. Specimens that are not fluorescent may become fluorescent after heating. |
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Not Radioactive |
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Optical Properties |
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Colorless, White, pale Blue, pale Violet, Mauve, Rose, pale Brown or dark Gray from included impurities. Colorless in transmitted light. |
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Transparent to Translucent |
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Pearly on {010}, Vitreous to Greasy on {001}; Vitreous on {100}. |
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1.567 - 1.618 Biaxial ( + ) |
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0.0420 - 0.0440 |
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Strong; r < v |
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Visible. Violet coloured material: X = colourless to very light yellow or rose; Y = light violet or rose; Z = violet. |
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Occurances |
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Geological Setting: |
A major component in sedimentary evaporite deposits and in the cap rocks above salt domes, commonly formed by dehydration of gypsum; in igneous rocks, fumarolic deposits, and in seafloor hydrothermal chimneys, also an alteration product in hydrothermal mineral deposits. |
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Common Associations: |
Gypsum, Halite, Sylvite, Polyhalite, Dolomite, Calcite, Magnesite, Celestine, Sulfur |
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Common Impurities: |
Sr, Ba, H2O |
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Type Locality: |
Salt mine, Hall, Innsbruck, Inn valley, North Tyrol, Tyrol, Austria |
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Year Discovered: |
1795 (or 1804) |
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View mineral photos: |
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Unusual Gem Categories |
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More Information |
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Anhydrite is a relatively common sedimentary mineral that is the result of dewatering of the rock forming mineral Gypsum (CaSO4 • 2H2O). Good crystal specimens of Anhydrite are extremely rare so faceted gems are also extremely rare. However, fine semi-translucent to opaque specimens of Anhydrite have been found in Mexico and Peru that have a fine blue color. This material is called Angelite for its "angelic" blue color. Anhydrite was named in 1804 by German geologist Abraham Gottlob Werner (1750 - 1817), from the Greek word anhydros meaning without water in allusion to the lack of water in its composition, in contrast to Gypsum,which contains water. Faceted gems, although extremely rare, are known from crystals found at Faraday Mine, Bancroft, Ontario, Canada; Leopoldshall, Stassfurt, Stassfurt Potash deposit, Saxony-Anhalt, Germany; and Simplon Railway Tunnel, Simplon Pass area, Brig, Wallis, Switzerland. These gems are pale purple and usually somewhat included. Blue Angelite is found at Naica, Mun. de Saucillo, Chihuahua, Mexico and Lima Department, Peru. |
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Anhydrite gems for sale: We have not photographed our Anhydrite gems yet. Please check back soon! |
