Name/Title
GypsumEntry/Object ID
2009.62.199Description
Chemical Composition: CaSO4*2H2O
Crystal System: Monoclinic System
Description: Common Name; Gypsum Rose
Chemistry; CaSO4*2H2O
Class: Sulfates
Location; Chihuahua, Mexico
PHYSICAL CHARACTERISTICS:
Color is usually white, colorless or gray, but can also be shades of red, brown and yellow.
Luster is vitreous to pearly especially on cleavage surfaces.
Transparency crystals are transparent to translucent.
Crystal System is monoclinic; 2/m
Crystal Habits include the tabular, bladed or blocky crystals with a slanted parallelogram outline. The pinacoid faces dominate with jutting prism faces on the edges of the tabular crystals. Long thin crystals show bends and some specimens bend into spirals called "Ram's Horn Selenite" Two types of twinning are common and one produces a "spear head twin" or "swallowtail twin" while the other type produces a "fishtail twin". Also massive, crusty, granular, earthy and fiberous.
Cleavage is good in one direction and distinct in two others..
Fracture is uneven but rarely seen.
Hardness is 2 and can be scratched by a fingernail.
Specific Gravity is approximately 2.3+ (light)
Streak is white.
Best Field Indicators are crystal habit, flexible crystals, cleavage and hardness.
Fracture: Uneven
Hardness: 2 Gypsum
Luster: Vitreous
Occurrence: Notable Occurances include Naica, Mexico; Sicily; Utah and Colorado, USA; and many other locallities throughout the world.
Rock Type: Sedimentary
Specific Gravity: 2..4
Streak: White
Variety: Gypsum has several variety names that are widely used in the mineral trade.
"Selenite" is the colorless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the greek for Moon and means moon rock.
Another variety is a compact fiberous aggregate called "satin spar" . This variety has a very satin like look that gives a play of light up and down the fiberous crystals.
A fine grained massive material is called "alabaster" and is an ornamental stone used in fine carvings for centuries, even eons.Collection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationLocation
Location
Shelf
CS-D-7Room
Curation StorageBuilding
Crater Rock MuseumCategory
StorageMoved By
CuratorDate
February 21, 2024Location
Drawer
North side 2nd leftShelf
Bottom Shelf, Bottom ShelfRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Joshua EspongeDate
November 13, 2009