mineral

Polished selenite (satin spar gypsum), likely carved/tumbled

Gypsum, CaSO₄·2H₂O; varietal identification is uncertain from the image

AI-generated identification · may be incorrect

White to translucent, pearly/satiny luster, Mohs hardness 2, very low specific gravity (~2.3), and perfect cleavage in one direction. The radial fan-like internal pattern and smooth rounded surface are consistent with polished gypsum, though white calcite is a possible alternative.

Identified September 12, 2026More mineral →

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At a glance

Common name: Polished selenite (satin spar gypsum), likely carved/tumbled
Scientific name: Gypsum, CaSO₄·2H₂O; varietal identification is uncertain from the image
Category: mineral
Identified: September 12, 2026
Method: Standard

AI Estimated Value

Approximately $2–$15 for a small polished specimen; exceptional large or naturally crystalized pieces may sell for $20–$100+.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Gypsum forms when sulfate-rich water evaporates in sedimentary basins, commonly during Permian to Cenozoic evaporite deposition. Selenite crystals can also form in caves and clay-rich lake deposits.

Uses & applications

Used for plaster, drywall, cement, fertilizer, and decorative specimens; carved pieces are sold as inexpensive collectibles. It is generally unsuitable for durable jewelry because it scratches and dissolves relatively easily.

Geological facts

Gypsum is one of the softest common minerals and can be scratched with a fingernail. A knife or copper coin can mark it, while dilute vinegar normally produces no strong fizz.

Field identification & locations

Confirm with a fingernail-scratch test and compare with calcite: calcite fizzes in dilute hydrochloric acid, whereas gypsum does not. Common sources include Mexico, Morocco, Spain, the United States, and Australia.