igneous
Likely olivine-rich peridotite or serpentinized ultramafic fragment
Olivine (forsterite–fayalite series), commonly with serpentine and pyroxene
AI-generated identification · may be incorrectSmall irregular green, granular specimen with dull to weakly vitreous luster; olivine hardness 6.5–7, serpentine 2.5–5.5, typically no obvious cleavage. Exact identification is limited by the photograph and lighting.
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Physical properties
Small irregular green, granular specimen with dull to weakly vitreous luster; olivine hardness 6.5–7, serpentine 2.5–5.5, typically no obvious cleavage. Exact identification is limited by the photograph and lighting.
Formation & geological history
Likely derived from Earth’s upper mantle and brought to the surface in ultramafic rocks, volcanic ejecta, or tectonic exposures; olivine formed by crystallization of Mg-rich magma, while serpentine results from later hydration. Ages vary widely by locality.
Uses & applications
Olivine is used in refractory materials, foundry sand, and occasionally jewelry as peridot; ordinary rock fragments have little commercial use.
Geological facts
Green color suggests olivine, but similar appearance can occur in serpentine, epidote, or green glass. A hardness or streak test would help distinguish them.
Field identification & locations
Check for granular crystals, glassy fracture, and resistance to scratching; olivine typically leaves a white streak and does not fizz with dilute acid. Common sources include Hawaii, Arizona, Pakistan, Norway, and serpentinite belts worldwide.
