Golden Duck Bill Selenite

Object/Artifact

-

Crater Rock Museum

Gypsum

Gypsum

Name/Title

Golden "Duck Bill" Selenite

Entry/Object ID

2009.62.118

Description

Chemical Composition: Hydrated Calcium Sulfate Crystal System: Monoclinic System Description: Common Name: Gypsum Chemistry: CaSO4-2(H2O), Hydrated Calcium Sulfate C: Sulfates Location: Manitoba, Canada Description: Spherical shaped cluster of twinned crystals, dark amber in color with three large twinned crystals jutting from the group, transparent with a slight hue of dark amber. 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: white

Collection

RAGM Mineral Collection

Acquisition

Accession

2009.62

Source or Donor

Museum Collection of Minerals

Acquisition Method

Donation

Dimensions

Width

5 in

Depth

3-3/4 in

Length

3-1/4 in

Weight

0.99 oz

Location

Location

Display Case

FS-9

Room

Frieda Smith Hall

Building

Crater Rock Museum

Category

Permanent

Moved By

Ian Cunningham

Date

December 27, 2023