A Geoscience Digital Image Library
A Geoscience Digital Image Library
| Title | Authigenic gypsum |
|---|---|
| Description | Gypsum is a hydrated calcium sulfate with the composition CaSO4•2H2O. It is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. The blades of gysum in the photograph formed as authigenic crystals (crystals that formed in place) in a glacial till. Typical gypsum is massive and fine grained. Fine grained varieties are called alabaster. Fibrous varieties are called satin spar. Coarser, clear bladed varieties are called selenite. The specimen of selenite is about 6.4 cm wide. Gypsum's name comes from the Greek, gyps meaning “burned” mineral. Selenite is in allusion to its pearly luster (moon light) on cleavage fragments. |
| Location | USA ▹ Minnesota ▹ Polk. Near Crookston. |
| Photographer | Shannon Heinle. 2001-06-05. |
| Collection | University of North Dakota Mineralogy Collection #786. |
| Key words | gypsum, selenite, sulfate, authigenic, alabaster, satin spar |
| Tech details | 420 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. |
| GeoDIL number | 630 |
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