metamorphic
Tumbled bronzite-bearing stone
Bronzite-rich serpentinite or pyroxenite; exact identification requires testing
AI-generated identification · may be incorrectDark brown-black, polished, with bronze-gold fibrous or granular areas and vitreous to greasy luster. Likely hardness about 5–6 Mohs; bronzite is orthorhombic pyroxene with two cleavages, while serpentinite is softer (2.5–5.5).
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Physical properties
Dark brown-black, polished, with bronze-gold fibrous or granular areas and vitreous to greasy luster. Likely hardness about 5–6 Mohs; bronzite is orthorhombic pyroxene with two cleavages, while serpentinite is softer (2.5–5.5).
Formation & geological history
Probably a polished/tumbled ultramafic rock formed deep in the mantle and later altered by hydrothermal fluids; commonly Precambrian to Phanerozoic in age depending on locality.
Uses & applications
Used as a decorative tumbled stone, lapidary material, and occasional ornamental stone; generally not valuable as a gemstone.
Geological facts
The bronze sheen is characteristic of bronzite, an iron-bearing magnesium silicate related to enstatite. The specimen may also contain serpentine, magnetite, or minor olivine.
Field identification & locations
Look for bronze chatoyancy or sparkles, dark green-black matrix, and unusually high density; a streak, hardness, specific-gravity, and magnetic test can distinguish bronzite-rich rock from dyed glass or slag. Common sources include Brazil, India, South Africa, Austria, and the USA.
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