metamorphic
Banded Serpentinite (Beach Pebble)
Serpentine-group silicate rock ((Mg,Fe,Ni,Al,Zn,Mn)3(Si,Fe,Al)2O5(OH)4)
Hardness: 3-6 on the Mohs scale. Color: Greenish-white to dark forest green and greyish-black bands. Luster: Waxy to resinous, dull when weathered. Texture: Smooth, rounded beach pebble. Specific Gravity: ~2.5-2.6.
- Hardness
- 3-6 on the Mohs scale
- Color
- Greenish-white to dark forest green and greyish-black bands
- Luster
- Waxy to resinous, dull when weathered
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Physical properties
Hardness: 3-6 on the Mohs scale. Color: Greenish-white to dark forest green and greyish-black bands. Luster: Waxy to resinous, dull when weathered. Texture: Smooth, rounded beach pebble. Specific Gravity: ~2.5-2.6.
Formation & geological history
Formed via serpentinization, a low-temperature metamorphic alteration process of mafic to ultramafic rocks (such as peridotite) rich in olivine and pyroxene, usually in ocean floor/subduction zone tectonic environments.
Uses & applications
Used primarily as decorative pebbles, tumbled stones, landscaping material, and carved ornaments or cabochons for jewelry.
Geological facts
Serpentinite is California's official state rock. It often feels slightly greasy or soapy to the touch due to its hydrated sheet silicate structure.
Field identification & locations
Identify in the field by its distinct pale to dark green coloration, waxy feel, and vein-like or banded metamorphic structures. Often found along coastal beaches and subduction zone complexes.
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