From: Ben Pittenger (benpittenger@earthlink.net)
Date: Tue Apr 16 2002 - 07:49:33 PDT
Date: Tue, 16 Apr 2002 07:49:33 -0700 From: Ben Pittenger<benpittenger@earthlink.net> Subject: Gypsum Message-ID: <Springmail.0994.1018968573.0.17481800@webmail.pas.earthlink.net>
It's been awhile since I was in my mineralogy classes. But I dug up a little about gypsum to confirm my memories. The term gypsum can mean either a naturally formed group of crystalline materials, or a wide variety of products manufactured from those natural sources.
In nature, gypsum is CaSO4, but with water. So it is called Hydrated Calcium Sulfate. It is found in areas where very salty waters have precipitated out minerals. It takes on a variety of appearances due to the presence of various other minerals, and/or water. It often forms fairly flat crystals, which look something like mica, but are not as smooth, thin, or flexible. Or it forms longer thin, fibrous crystals that can be bunched together like a wild pincushion, or gathered together in a dense, parallel pattern.
Alabaster (the sculpting material) is a form of gypsum. We make plaster of paris and wallboard from ground gypsum. It's also added to cement to affect the curing time.
Some sources:
http://www.minerals.net/mineral/sulfates/gypsum/gypsum.htm
http://mineral.galleries.com/minerals/sulfates/gypsum/gypsum.htm
http://minerals.usgs.gov/minerals/pubs/commodity/gypsum/ (Hooray for the USGS!)
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