Hydrated calcium sulfate and one of the most common evaporite minerals. Defines hardness 2 on the Mohs scale. Used to make plaster. Color: Colorless, white, gray, yellowish. Luster: Vitreous to silky. Streak: White. Cleavage: Perfect in one direction. Hardness: 2. Transparency: Transparent to translucent. Crystal system: Monoclinic. Chemical formula: CaSO₄·2H₂O. Specific gravity: 2.31-2.33. Formation: Precipitates from evaporating seawater and saline lakes. Also forms as an alteration product of sulfide minerals. Common geological settings: Worldwide; found in evaporite sequences, desert roses, and selenite crystal caves Naica, Mexico . Common look-alikes and related entries: Calcite, Anhydrite, Selenite.
White minerals — Place this specimen in a broader field-identification workflow.
Gypsum vs Calcite — Compare observable properties and safer field tests.
Sources, scope & corrections
These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
Editorial owner
GeoMiner
Last updated
2026-03-30T14:37:03.104701+00:00
Review status
Published; not independently peer-reviewed
IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
Hydrated calcium sulfate and one of the most common evaporite minerals. Defines hardness 2 on the Mohs scale. Used to make plaster.
How can you identify Gypsum?
Compare several properties rather than relying on colour alone. This entry records colour: Colorless, white, gray, yellowish; lustre: Vitreous to silky; streak: White; Mohs hardness: 2; cleavage: Perfect in one direction; crystal system: Monoclinic; transparency: Transparent to translucent. Confirm an important identification with additional field tests or qualified laboratory work.
How does Gypsum form?
Precipitates from evaporating seawater and saline lakes. Also forms as an alteration product of sulfide minerals.
Where is Gypsum commonly found?
Worldwide; found in evaporite sequences, desert roses, and selenite crystal caves Naica, Mexico .
What is Gypsum commonly confused with?
Gypsum may be confused with Calcite, Anhydrite, Selenite. Compare multiple diagnostic properties because colour and surface appearance can overlap.
JavaScript is loading the interactive GeoMiner experience. The identification tools provide educational candidates, not laboratory confirmation.
