mineral

Dark blue-black polished crystal, likely fluorite or slag-like geological material

Tentatively fluorite (CaF₂); identification is uncertain from the image alone

AI-generated identification · may be incorrect

Opaque to translucent dark blue-black, vitreous to subvitreous luster, with a faceted or naturally terminated shape and possible surface inclusions. Fluorite has Mohs hardness 4, cubic crystals, perfect octahedral cleavage, and specific gravity about 3.18; color alone is not diagnostic.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

If fluorite, it formed in hydrothermal veins and cavities, commonly with quartz, calcite, or sulfides; deposits range from Precambrian to Cenozoic. The visibly shaped surface may indicate cutting or polishing rather than a natural crystal form.

Uses & applications

Fluorite is used industrially as a flux and source of fluorine, and attractive transparent pieces are collected or cut as gemstones. This specimen appears more suitable for casual collecting than jewelry.

Geological facts

Dark fluorite can resemble obsidian, tourmaline, or industrial slag. Fluorite’s cubic cleavage and relatively low hardness are useful distinguishing features.

Field identification & locations

Common sources include China, Mexico, the United States, England, and South Africa. Test cautiously: fluorite scratches with a steel knife but not glass; definitive identification requires cleavage, density, fluorescence, or analytical testing.