Selenite

Object/Artifact

-

Crater Rock Museum

Name/Title

Selenite

Entry/Object ID

78.63.295

Description

Chemical Composition: CaSO4-2H2O Crystal System: Monoclinic System Description: Common Name:Selenite Group Name: Sulfates Chemistry: CaSO4-2H2O Location: Unknown Description: A large crystal of Selenite(Gypsum). Colors: Long crystal with perfect cleavage in two sickles,in honey colored with rough sides on two sides.Interior contains some hair-like formations. Physical Characteristics: Composition Hydrous calcium sulfate Color Colorless, white, gray, brown, beige, orange, pink, yellow, light red, green Streak White Hardness 2 Crystal System Monoclinic 3D Crystal Atlas (Click for animated model) Monoclinic Tabular Contact Swallowtail Twin Complex Tabular Penetration Twin Crystal Forms and Aggregates Commonly occurs as tabular crystals, sometime perfect with no imperfections. Also occurs prismatic, acicular, bladed, and as dense bundles of fragile acicular crystals. Other forms are as fibrous veins, scaly, grainy, lenticular, rosette, massive, and as parallel, cactus-like growths. Crystals and fibrous masses may be curved, sometimes severely, forming formations that are sometimes called "Rams Horns". Crystals frequently twin, forming perfect fishtail twins or swallowtail twins. Crystals can be enormous in size. In fact, the largest crystals ever found on earth were of Gypsum. Transparency Transparent to opaque Specific Gravity 2.3 - 2.4 Luster Vitreous to pearly Cleavage 1,1 - micaceous ; 2,2 Fracture Uneven Tenacity Sectile and slightly flexible Other ID Marks Often fluorescent light yellow in shortwave ultraviolet light, and occasionally also phosphorescent. In Group Sulfates; Hydrous Sulfates Striking Features Crystal habits, low hardness, flexibility, and sectility Environment In enormous deposits and beds in sedimentary rock, specifically limestone. Also in clay sedimentary deposits, and in dry caves. Occasionally also in igneous traprock and in the oxidation zone of sulfide deposits. Rock Type Igneous, Sedimentary Popularity (1-4) 1 Prevalence (1-3) 1 Demand (1-3) 1 Gypsum ON - See more at: http://www.minerals.net/mineral/gypsum.aspx#sthash.NhsKgv5t.dpuf Fracture: Uneven Hardness: 2 Gypsum Luster: Vitreous Rock Type: Sedimentary Specific Gravity: 2.3-2.7 Streak: white

Collection

Delmar Smith Crystal Collection

Acquisition

Accession

78.63.295

Dimensions

Width

1 in

Depth

1-1/4 in

Length

8-3/8 in

Dimension Notes

Dimension taken at widest points

Location

Location

Shelf

CS-D-2

Room

Curation Storage

Building

Crater Rock Museum

Category

Storage

Moved By

Curtis Gardner

Date

January 3, 2024