metamorphic
Serpentine (Serpentinite)
Antigorite, Lizardite, and Chrysotile: (Mg,Fe)3Si2O5(OH)4
Hardness: 3–6 (Mohs scale); Color: Variegated dark green to nearly black with lighter green mottling/veining; Luster: Waxy, greasy, or silky; Crystal structure: Monoclinic; Cleavage: Poor to perfect depending on mineral type; Specific Gravity: 2.5–2.8.
- Hardness
- 3–6 (Mohs scale)
- Luster
- Waxy, greasy, or silky
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Physical properties
Hardness: 3–6 (Mohs scale); Color: Variegated dark green to nearly black with lighter green mottling/veining; Luster: Waxy, greasy, or silky; Crystal structure: Monoclinic; Cleavage: Poor to perfect depending on mineral type; Specific Gravity: 2.5–2.8.
Formation & geological history
Formed via hydration of ultramafic rocks (like peridotite) in the Earth's mantle or oceanic crust, a process called serpentinization. This typically occurs at low temperatures and high pressures in subduction zones.
Uses & applications
Used as an ornamental stone in architecture, sculptures, and jewelry (as 'New Jade'). Historically used for asbestos production (chrysotile), though this is now restricted due to health risks.
Geological facts
Serpentine is the official state rock of California. It is famous for its 'snake-skin' appearance, which is how it earned its name. It often contains microscopic fibers of asbestos.
Field identification & locations
Identify by its characteristic 'greasy' or waxy feel and mottled green patterns. In the field, look for 'slickensides' (polished surfaces) in tectonic suture zones. Common in California, the Alps, and the Himalayas.
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