metamorphic
Greenstone / Serpentinite
Serpentinite (complex of Mg, Fe, Ni, Al, Zn, Mn silicate minerals including Antigorite, Lizardite, and Chrysotile)
Hardness: 2.5–6 on Mohs scale; Color: typically dark green, grayish-green, or blackish-green with a mottled appearance; Luster: waxy to greasy; Structure: massive to fibrous; Cleavage: poor; Specific Gravity: 2.5–2.6.
- Hardness
- 2
- Luster
- waxy to greasy
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Physical properties
Hardness: 2.5–6 on Mohs scale; Color: typically dark green, grayish-green, or blackish-green with a mottled appearance; Luster: waxy to greasy; Structure: massive to fibrous; Cleavage: poor; Specific Gravity: 2.5–2.6.
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rock (peridotite) from the Earth's mantle, typically at tectonic plate boundaries (subduction zones). It often represents ancient seafloor brought to the surface.
Uses & applications
Used as a decorative building stone, in jewelry (often as a jade simulant), and historically as a source of asbestos. High-quality varieties are used for carving.
Geological facts
Serpentinite is the state rock of California. The process of its formation, serpentinization, can produce hydrogen and methane which may support microbial life in extreme environments.
Field identification & locations
Look for a distinctive 'snake-skin' pattern, a greasy or soapy feel, and a dark green color. It is often found in ophiolite complexes near major fault zones and coastal mountains.
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