mineral

Rainbow carborundum (silicon carbide)

Silicon carbide, SiC; commonly synthetic moissanite/carborundum specimen

AI-generated identification · may be incorrect

Very dark gray to black with intense iridescent blue, purple, green, and gold surfaces from thin-film oxidation; metallic to adamantine luster. Mohs hardness 9–9.5, typically granular or hexagonal/polytypic crystals, with uneven fracture and specific gravity about 3.2.

Identified September 20, 2026More mineral →

Explore Rainbow carborundum (silicon carbide) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Most decorative specimens are laboratory-grown silicon carbide, often produced industrially in electric furnaces at very high temperatures rather than formed naturally. Natural moissanite is exceptionally rare and occurs mainly in meteorites and a few ultramafic terrestrial rocks.

Uses & applications

Used industrially as an abrasive, refractory, semiconductor, and ceramic; gem-quality synthetic SiC is sold as moissanite. Iridescent clusters are popular mineral-shop and teaching specimens.

Geological facts

The rainbow sheen is usually caused by oxidation films or surface coatings, not inherent crystal color. Silicon carbide is nearly as hard as diamond and has many crystal polytypes.

Field identification & locations

Identify by its black, extremely hard, angular crystals and vivid iridescence; avoid confusing it with coated quartz or slag, since tests can damage the specimen. Common commercial sources include China and laboratory manufacturers.