Name/Title
Selenite on HaliteEntry/Object ID
2004.1.99Description
Assemblage Zone: pegmatite dikes
Chemical Composition: CaSO4*2H2O
Crystal System: Monoclinic System
Description: Common Name:Gypsum
Group Name:
Chemistry: CaSO4*2H2O
Location: Peru
Description: Spikey white 'balls' of crystals growing out of tannish-brown bed of slab-like crystals.
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: Color is pink or white; also tinted yellow and red.
Luster is vitreous to pearly especially on the prominant pinacoid and cleavage surfaces.
Transparency: crystals are transparent to mostly translucent.
Crystal System is monoclinic; 2/m
Crystal Habits include platy often thin crystals that can aggregate together into a wheat sheaflike structure. The prominant pinacoid is sometimes but rarely modified by other pinacoid and prism faces. Cruciform (cross-like) twins can also be found. Also forms radiating nodules.
Cleavage is perfect in one direction parallel to the prominant pinacoid.
Fracture is uneven.
Hardness is 3.5 - 4.
Specific Gravity is approximately 2.2 (very light)
Streak is white.
Associated Minerals are quartz, calcite, babingtonite, apophyllite, heulandite, natrolite and other zeolites.
Notable Occurrences include Poona, India; Scotland; Iceland; New Jersey and Stilbite is a common and perhaps the most popular zeolite mineral for collectors. Stilbite crystals can aggregate together to form a structure resembling wheat sheafs. This hourglass structure looks like several crystals stacked parallel to each other with the tops and bottoms of this structure fanning out while the middle remains thin. Stilbite's hallmark crystal habit is unique to stilbite and a rarer but related zeolite called stellerite. Whether in the wheat sheafs or not, stilbite can be a hansome specimen with its pearly luster and often colorful pink tints. Stilbite commonly forms nice crystals inside the petrified bubbles (called vesicles) of volcanic rocks that have undergone a small amount of metamorphism.
Notable Occurrences include Poona, India; Scotland; Iceland; New Jersey and Nova Scotia, Canada.
Rock Type: Sedimentary
Specific Gravity: 2.3
Streak: white
Texture: cryastaline
Variety: Gypsum 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. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.
Notable Occurances include Naica, Mexico; Sicily; Utah and Colorado, USA; and many other locallities throughout the world.Collection
Suomynona Mineral Collection, Suomynona CollectionAcquisition
Accession
2004.1Source or Donor
Suomynona Mineral CollectionAcquisition Method
DonationDimensions
Width
8 inDepth
5 inLength
9 inWeight
3.72 ozDimension Notes
Dimension taken at widest pointsLocation
Location
Wall
CenterBuilding
Freida Smith HallCategory
PermanentMoved By
Steve MillerDate
June 18, 2013Location
Container
CenterDrawer
3rd ShelfShelf
right, rightWall
SouthRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Steve MillerDate
October 4, 2012Location
Drawer
rightShelf
top, topWall
east wallBuilding
Frieda L Smith HallCategory
PermanentMoved By
Scott LonganDate
August 25, 2009Location
Container
LeftDrawer
2nd ShelfShelf
Left, LeftWall
NorthBuilding
Frieda L Smith HallCategory
PermanentMoved By
Wendy MondryDate
August 25, 2009Location
Container
RightDrawer
2nd ShelfShelf
Left, LeftWall
NorthBuilding
Frieda L Smith HallCategory
PermanentMoved By
Wendy MondryDate
August 25, 2009Location
Drawer
MiddleShelf
TopCabinet
Case #26Wall
Back WallRoom
Freida HallBuilding
Freida Smith HallCategory
Permanent
