A lump of
fine grained Alabaster.
A
well formed, clear crystal of Gypsum from Canada. The clear variety of
Gypsum is called Selenite.
This is the fibrous variety of Gypsum called Satin Spar. This specimen is
from the Verde Valley of Arizona.
Selenite Rose MMT ___ This pair of pictures shows the front and back side of the
specimen. Locality: Tunisia, Algeria.
Gypsum Crystal AMMM
collection. Specimen is from Utah.
CHEMISTRY CaSO4 .H2O Hydrous calcium sulfate
CRYSTALLOGRAPHY Monoclinic
CRYSTAL GROWTH AND HABITS Gypsum crystals are prismatic to tabular and commonly form "fish tail" twins.
COLOR AND OTHER OPTICAL PROPERTIES Clear to white or brownish
HARDNESS 2
SPECIFIC GRAVITY 2.32
LUSTER Vitreous to earthy
STREAK White
BREAKABILITY Gypsum has 3 directions of cleavage, one is nearly perfect like mica and produces thin sheets. The thin sheets are flexible but not elastic like mica. Gypsum is also sectile.
OCCURRENCE Gypsum is very common as sedimentary rock produced by the evaporation of water (evaporite). It is also found in association with fumerolic gases.
ASSOCIATED MINERALS Anhydrite, Calcite, Dolomite