gypsum - satin spar variety of gypsum from Morocco - long display specimen
Gypsum - variety satin spar hydrated calcium sulfate CaSO4∙2H2O
Satin spar is the fibrous crystal form of gypsum. It has a silky luster and often forms in veins. Gypsum is widely distributed in sedimentary rocks, often as thick evaporite beds. It is one of the first minerals to crystallize by chemical precipitation as salt water evaporates.
The primary economic use of gypsum is in the manufacture of plaster, where it is powdered and heated to about 150˚C to drive off the water. When water is added to plaster, it rehydrates to form gypsum again.
We were given a locality in Morocco for this satin spar, but as is occasionally the case with Moroccan specimens, it has been impossible to confirm. This satin spar has very fine fibers and was cleaved from a large block. The pencil is 5 1/2" long, for scale.
Select a specimen: When more than one specimen is shown, you can select a particular specimen by telling us what is in the photo with it, a blue or black and silver pen, a black mechanical pencil or one of those plus some number of coins, or you can let us make the selection.
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