mineral

Bismuth Crystal

Bismuth (Bi)

Hardness: 2.25 on Mohs scale; Color: Iridescent rainbow colors (due to oxidation) over a silvery-white base; Luster: Metallic; Crystal Structure: Trigonal (often forming laboratory-grown hopper crystals); Cleavage: Perfect; Specific Gravity: 9.78

Hardness: 2
Luster: Metallic

Identified July 20, 2026More mineral →

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Physical properties

Formation & geological history

While naturally occurring at very low abundances in the Earth's crust, these colorful hopper crystals are typically lab-grown by melting high-purity bismuth and allowing it to cool slowly, which causes the edges to grow faster than the faces.

Uses & applications

Used in cosmetics (bismuth oxychloride), pharmaceuticals (Pepto-Bismol), low-melting alloys, lead-free solders, and as a popular collector's specimen.

Geological facts

Bismuth is one of the few substances, like water, that expands as it freezes from a liquid to a solid. The rainbow colors are actually an 'interference' effect created by a thin layer of bismuth oxide on the surface.

Field identification & locations

Identified by its unique 'stair-step' hopper crystal shape and brilliant iridiscence. In nature, it usually appears as dull, massive, or foliated metallic grey chunks rather than these geometric rainbow shapes.