Mineral description : Gypsum

Small crystals of gypsum from Kvinnesta.

Mineral class Sulphates : Anhydrite - Gypsum group.
Chemical formula Ca(SO4).2H2O
Crystal system Monoclinic.
Habitus Tabular or elongated crystals. Aggregates in the form of roses are called desertroses. Also radiating fibric aggregates. Twinning is common in the form of swallow tails. Grainy or compact aggregates are also common.
Cleavage Perfect, creating thin fragments.
Hardness 2
Density 2.35
Color White to yellowish white.
Streak  
Luster Vitreous to pearly. Transparent to translucent.
Description  
Occurance In evaporite deposits or deposits around hot springs.
In Sweden the main occurance is in old mine dumps and mineshafts. A product from oxidised pyrite.
Associates  
Notes Transparent crystals and fragments are called selenite.
Dense banded varietys are called alabaster.
Soluble in hydrochloric acid and hot water.
Could show fluorescens.
Locations Common on old mine dumps at sulphide mines.
  • Falu mine, Dalarna. On the walls of old mine shafts.
  • Stollgruvan, Västra Silfberg, Dalarna. In the dump pile of sulphide ore.
  • Solberga Limestone quarry, Boda, Dalarna. On the walls, resulting from oxidation of marcasite.
  • Långban, Värmland. As fracture fillings.
  • Harstigen, Persberg, Värmland. As fracture fillings.

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axelsson@acc.umu.se
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Last changed : 1998-09-09