metamorphic
Serpentine / Serpentinite
Serpentine group ((Mg,Fe,Ni,Al,Zn,Mn)3(Si,Al)2O5(OH)4)
Hardness: 3 to 6 on Mohs scale. Color: Dark green to greyish-green with mottled blackish veining. Luster: Waxy, greasy, or silky when wet/polished. Cleavage: Poor to non-existent; microcrystalline or fibrous mass. Specific gravity: 2.5 to 2.6.
- Hardness
- 3 to 6 on Mohs scale
- Color
- Dark green to greyish-green with mottled blackish veining
- Luster
- Waxy, greasy, or silky when wet/polished
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Physical properties
Hardness: 3 to 6 on Mohs scale. Color: Dark green to greyish-green with mottled blackish veining. Luster: Waxy, greasy, or silky when wet/polished. Cleavage: Poor to non-existent; microcrystalline or fibrous mass. Specific gravity: 2.5 to 2.6.
Formation & geological history
Formed through hydrothermal alteration (serpentinization) of mafic to ultramafic igneous rocks like peridotite in oceanic crust and subduction zone environments.
Uses & applications
Used as decorative stone, lapidary carving, architectural facing, and historically as a source of asbestos (chrysotile varieties). Popular for beachcombers and rock collectors.
Geological facts
Serpentine is California's official state rock. The process of serpentinization releases hydrogen gas and creates unique alkaline environments that can support extremophile life forms.
Field identification & locations
Identified by its distinctive smooth, waxy feel, characteristic greasy luster, and mottled dark green-black swirled patterns. Widely found along ocean beaches near subduction zone terranes like coastal California, Oregon, Greece, and New Zealand.
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