mineral

Selenite (Satin Spar)

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: White, pearly, or colorless. Luster: Silky or pearly. Crystal structure: Monoclinic, often fibrous. Cleavage: Perfect in one direction. Specific gravity: 2.3.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: White, pearly, or colorless
Luster: Silky or pearly

Identified June 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, often resulting from the evaporation of seawater or in clay beds and caves. Found in deposits ranging from ancient Paleozoic to recent formations.

Uses & applications

Used in the manufacture of plaster of Paris, wallboard (drywall), and cement. In the lapidary world, it is popular for ornamental carvings, lamps, and as decorative healing crystals.

Geological facts

Selenite is named after the Greek word 'selēnitēs', meaning 'moon-stone' because of its pale moonlight-like glow. The Naica Mine in Mexico contains giant selenite crystals measuring up to 39 feet in length.

Field identification & locations

Identify in the field by its extreme softness and fibrous luster. It is highly soluble in water and can be scratched with a fingernail. Common locations include Morocco, Mexico, USA (Utah/New Mexico), and Brazil.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

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Schist

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Nephrite Jade

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Biotite Schist

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