Mineral Set #2: Halides and Evaporites:
|
Mineral |
Formula |
Crystal System |
Other Properties |
|
Halite |
NaCl |
Cubic |
Cubic cleavage; salty taste |
|
Sylvite |
KCl |
Cubic |
Bitter taste |
|
Fluorite |
CaF2 |
Cubic |
Hardness 4; octohedral cleavage; thermoluminescent; sometimes fluorescent |
|
Gypsum |
CaSO4•H2O |
Monoclinic |
Three common habits: Alabaster (Massive) Satin Spar (Fibrous) Selenite (Clear crystals) |
|
Anhydrite |
CaSO4 |
Orthorhombic |
Usually massive and blue |
|
Barite |
BaSO4 |
Orthorhombic |
Unusually dense; forms Desert Rose twinned crystals |
|
Celestite |
SrSO4 |
Orthorhombic |
Also occurs with limestones |
|
Borax |
CaB4O5(OH)2•8H2O* |
Monoclinic |
|
|
Kernite |
Na2(B4O6(OH)2)•3H2O |
Monoclinic |
"satiny" appearance |
|
Colemanite |
Ca(B3O4(OH)3)•H2O |
Monoclinic |
Occurrences: in playa lakes and other sites of extensive evaporation. All these minerals form when soluble ions are leached into solution via rainfall associated weathering, and these waters congregate in lacustrine basins in arid environments