Angelite/Anhydrite
Angelite/Anhydrite Category – Sulfate Mineral Chemical Formula Anhydrous calcium sulfate: CaSO4 Crystal Symmetry – Orthorhombic – massive Color – Colorless to pale blue or violet if transparent; white, mauve, rose, pale brown or gray from included impurities. Crystal Habit – Rare tabular and prismatic crystals. Usually occurs as fibrous, parallel veins that break off into cleavage fragments. Also occurs as grainy, massive, or nodular masses Crystal System – Orthorhombic Geography – Mexico, Peru Mohs scale - 3.5 Luster Pearly, vitreous to greasy Streak - white Other Characteristics – Some specimens fluoresce; many more fluoresce after heating. Anhydrite is calcium sulfate. The Calcium Sulfate forms from water loss in gypsum. The gypsum shrinks over time, making the structure of anhydrite opaque and compact. Anhydrite was first discovered, in 1794, in a salt mine near Hall in Tirol, Austria. In this occurrence depth is critical since nearer the surface anhydrite has been alt