Name/Title
GypsumEntry/Object ID
2009.62.124Description
Chemical Composition: Hydrated Calcium Sulfate
Crystal System: Monoclinic System
Description: Common Name: Gypsum
Chemistry: CaSO4-2(H2O), Hydrated Calcium Sulfate
Class: Sulfates
Location: Weisssshan, Yunnan, China
Description: Very large specimen with approximately six highly elongated transparent crystals extending from a multi-structured base including a druzy white crystalline structure mixed with a dull, white, cotton-ball like crystalline structure on a dull white and tan granular matrix.
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.
Associated Minerals are halite, calcite, sulfur, pyrite, borax and many others.
Other Characteristics: thin crystals are flexible but not elastic, meaning they can be bent but will not bend back on their own. Also some samples are fluorescent. Gypsum has a very low thermal conductivity (hence it's use in drywall as an insulating filler). A crystal of Gypsum will feel noticeably warmer than a like crystal of quartz.
Best Field Indicators are crystal habit, flexible crystals, cleavage and hardness.
Fracture: uneven
Hardness: 2 Gypsum
Luster: Vitreous
Occurrence: Deposits are known to occur in strata from as early as the Permian age.[5] Gypsum is deposited in lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins. Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near surface exposures. It is often associated with the minerals halite and sulfur.
Rock Type: Sedimentary
Specific Gravity: 2.3
Streak: whiteCollection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Width
9-1/2 inDepth
7 inLength
9-1/4 inWeight
13.33 ozLocation
Location
Wall
CenterBuilding
Freida Smith HallCategory
PermanentMoved By
Steve MillerDate
June 18, 2013Location
Container
CenterDrawer
Bottom / BackShelf
Left, LeftWall
West wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Steve MillerDate
January 26, 2010Location
Drawer
3nd from the leftShelf
bottom back left, bottom back leftWall
West wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Jacob RierDate
September 26, 2009Location
Drawer
LeftShelf
BottomCabinet
Case #27Wall
Back WallRoom
Freida HallBuilding
Freida Smith HallCategory
Permanent
