metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals usually (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4)
Hardness: 2.5-6 on Mohs scale; Color: typically green to yellow-green, sometimes brownish or black; Luster: waxy, greasy, or silky; Crystal structure: Monoclinic; Cleavage: poor/basal; Specific gravity: 2.2-2.9
- Hardness
- 2
- Color
- typically green to yellow-green, sometimes brownish or black
- Luster
- waxy, greasy, or silky
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Physical properties
Hardness: 2.5-6 on Mohs scale; Color: typically green to yellow-green, sometimes brownish or black; Luster: waxy, greasy, or silky; Crystal structure: Monoclinic; Cleavage: poor/basal; Specific gravity: 2.2-2.9
Formation & geological history
Formed by the hydration of ultramafic rocks (like peridotite) from the Earth's mantle through a process called serpentinization at low-to-moderate temperatures and high pressures, often at tectonic plate boundaries.
Uses & applications
Used as an architectural stone (terrazzo tile, cladding), for stone carvings (jade substitute), and historically as a source of asbestos. High-quality varieties are used in jewelry.
Geological facts
Serpentinite is the official state rock of California. Its formation can release hydrogen gas, which can support unique microbial ecosystems in the deep ocean and underground.
Field identification & locations
Identify in the field by its distinct waxy green appearance and 'slippery' soapy feel. It is commonly found in ophiolitic belts, such as the Coast Ranges of California, the Alps, and the Himalayas.
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