igneous
Olivine-rich pebble (likely peridotite fragment)
Olivine, chiefly forsterite–fayalite solid solution; possible dunite/peridotite
AI-generated identification · may be incorrectSmall, olive-green, granular fragment with a dull to slightly glassy luster; olivine hardness is 6.5–7 Mohs, no prominent cleavage, and specific gravity about 3.2–4.4. The photograph is insufficient to confirm mineral identity or texture.
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Physical properties
Small, olive-green, granular fragment with a dull to slightly glassy luster; olivine hardness is 6.5–7 Mohs, no prominent cleavage, and specific gravity about 3.2–4.4. The photograph is insufficient to confirm mineral identity or texture.
Formation & geological history
Likely crystallized deep in the mantle from ultramafic magma, then exposed by tectonic uplift and erosion; mantle rocks are commonly Paleozoic or older, though age cannot be determined visually.
Uses & applications
Gem-quality transparent olivine is peridot; ordinary material is mainly a collector specimen or indicator of ultramafic geology, with limited refractory and industrial use.
Geological facts
Olivine commonly alters to serpentine, producing green, brown, or rusty surfaces. Its olive color and relatively high density are characteristic, but similar green rocks include serpentine, epidote, and weathered basalt.
Field identification & locations
Look for granular olive-green material, high density, and glassy grains; a streak, hardness, density, and microscope test would help distinguish it. Common sources include peridotite massifs, volcanic rocks, and basaltic lava deposits.
