Gypsum

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Gypsum is a mineral that has been utilized since antiquity. This soft mineral represents the second level on the Mohs hardness scale. Cut stones are rare because gypsum has perfect cleavage, and it is too soft to facet. The fine-grained variety known as alabaster is used for carvings and decorative objects. Selenite is the large crystalline variety that is popular with mineral collectors. The fibrous variety is known as satin spar. Gypsum sometimes crystallizes in rosette patterns known as desert roses. Gypsum is probably best known for its use in construction materials like sheetrock, cement, and plaster.

Gypsum Rough
Gypsum Classification
Common Name Gypsum
Species Gypsum
Gypsum Optical Properties
Transparency Opaque-Transparent
Dispersion Strength: Strong Fire
Refractive Index 1.519-1.530
Birefringence 0.009- 0.010
Optic Character Biaxial
Optic Sign Positive
Polariscope Reaction Aggregate (AGG), Doubly Refractive (DR)
Fluorescence SWUV: Typically bluish white but can be yellowish green, green, bluish white, greenish white, pinkish white, yellowish white, white, pale yellow, yellow
LWUV: Typically yellowish white but can be green, greenish white, yellowish white, bluish white, pale yellow, orange yellow
Pleochroism None
Gypsum Characteristic Physical Properties
Hardness 1.5-2
Streak White
Specific Gravity 2.200-2.400
Toughness Poor
Luster Vitreous, Dull, Waxy, Silky, Pearly
Fracture Granular, splintery and conchoidal
Cleavage Perfect
Gypsum Chemistry & Crystallography
Chemical Name Hydrated calcium sulfate
Chemical Formula CaSO4.2H2O
Crystal System Monoclinic
Chemistry Classification Sulfate

Gypsum Colors

  • Black Gypsum Black
  • White Gypsum White
  • Colorless Gypsum Colorless
  • Yellow Gypsum Yellow
  • Brown Gypsum Brown
  • Blue Gypsum Blue
  • Pink Gypsum Pink
  • Gray Gypsum Gray

Alternate Names

Alabaster, Desert Rose, Gypsite, Satin Spar, Selenite

Countries of Origin

Niger (the); Papua New Guinea; Angola; Kazakhstan; Paraguay; Portugal; Moldova (the Republic of); Solomon Islands; Greece; Latvia; Mongolia; Morocco; Panama; Chile; Argentina; Isle of Man; Ukraine; Zambia; India; Canada; Turkey; Belgium; Namibia; Finland; South Africa; Georgia; Peru; Turkmenistan; Venezuela (Bolivarian Republic of); Germany; Yemen; Tanzania, United Republic Of; United Arab Emirates (the); Eritrea; Fiji; Madagascar; Thailand; Kiribati; Libya; Costa Rica; Sweden; Liechtenstein; Russian Federation (the); Poland; Jordan; Tunisia; Palestine, State of; Croatia; Syrian Arab Republic; Tuvalu; Kenya; Switzerland; Spain; Djibouti; Lebanon; Azerbaijan; Cuba; Mauritania; Saint Lucia; Lao People's Democratic Republic (the); Australia; Tajikistan; Estonia; Myanmar; Cyprus; Malaysia; Iceland; Oman; Bosnia And Herzegovina; Armenia; Austria; Mozambique; Korea (the Republic of); Luxembourg; Brazil; Algeria; Slovenia; Colombia; Ecuador; United States of America (the); Hungary; Japan; Taiwan (Province of China); Albania; Bolivia (Plurinational State of); Trinidad And Tobago; New Zealand; Vanuatu; Senegal; Italy; Antarctica; Ethiopia; Afghanistan; Czechia; Egypt; Malta; Saudi Arabia; Pakistan; China; Ireland; Qatar; Sudan (the); Slovakia; France; Lithuania; Serbia; Bahamas (the); Kyrgyzstan; Bhutan; Romania; Dominican Republic (the); Uzbekistan; Netherlands (the); Barbados; Nicaragua; Norway; Botswana; Denmark; Mexico; Zimbabwe; Philippines (the); Greenland; Montenegro; Indonesia

Care

Due to its soft nature gypsum needs to be kept away from harder materials that will damage its surface. Gypsum will turn cloudy if exposed to heat.

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Species/Variety

Alabaster

Alabaster is a fine-grained massive form of gypsum. Alabaster ranges from white to yellow, pink, and brown. Due to its porosity it is often dyed. It has been used for centuries for statues, carvings, and other ornamental purposes. Treated alabaster is used as a marble simulant. Due to its extreme softness, it is ideal for fashioning into works of art.

Alabaster Gypsum
Alabaster Classification
Common Name Alabaster
Alabaster Characteristic Physical properties
Specific Gravity 2.250
Toughness Poor
Stability Poor

Satin Spar

Satin spar is an adjective used when the fibrous habit of a mineral gives it a satin luster. The term satin spar has been used in the past to describe calcite and aragonite; however, it is currently accepted as one variety of the mineral gypsum, along with selenite and alabaster.

Satin Spar Gypsum
Satin Spar Classification
Common Name Satin Spar
Satin Spar Optical Properties
Refractive Index 1.52-1.529
Tolerance:(+0.001/-0.001)
Birefringence 0.009-0.01
Fluorescence SWUV: Inert to weak brownish to greenish white
LWUV: Inert to weak brownish to greenish white
Satin Spar Characteristic Physical properties
Specific Gravity 2.25
Inclusions Satin spar is a white to cream fibrous gypsum with chatoyant effect.
Stability Fair

Desert Rose

When gypsum forms in rose like patterns it is called a desert rose. They are found in desert regions where liquid containing gypsum evaporates leaving the gypsum to crystallize. Gypsum roses can be distinguished from barite roses by their sharp edges. Desert roses from Chihuahua, Mexico have distinctive white edges.

Desert Rose Gypsum
Desert Rose Classification
Common Name Desert Rose
Desert Rose Characteristic Physical properties
Toughness Poor
Stability Poor

Selenite

Selenite is the name for transparent, colorless to near colorless crystals of gypsum, a hydrous calcium sulfate that is found in a number of forms. The name "selenite" comes from the Greek word selene, meaning "moon", no doubt in reference to the gem's white glow. Gypsum, in all varieties, is very soft and has perfect cleavage so it should be handled with care.

Selenite Gypsum
Selenite Classification
Common Name Selenite
Selenite Characteristic Physical properties
Specific Gravity 2.250
Stability Poor
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Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.