metamorphic
Serpentinite
Serpentinite (composed primarily of Antigorite, Lizardite, or Chrysotile)
Hardness: 3 to 6 on Mohs scale; Color: Shades of green from light to dark, sometimes blackish or yellowish; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic or Orthorhombic (microcrystalline); Cleavage: Poorly defined
- Hardness
- 3 to 6 on Mohs scale
- Luster
- Waxy, greasy, or silky
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Physical properties
Hardness: 3 to 6 on Mohs scale; Color: Shades of green from light to dark, sometimes blackish or yellowish; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic or Orthorhombic (microcrystalline); Cleavage: Poorly defined
Formation & geological history
Formed through the metamorphic process known as serpentinization, where ultramafic rocks (like peridotite) from the Earth’s mantle are altered by hydrothermal fluids at low temperatures and high pressures, often at tectonic boundaries.
Uses & applications
Used as decorative building stone, in high-end countertops, as a source for magnesium, and historically as a source for carving and asbestos (though most modern uses avoid asbestiform varieties).
Geological facts
It is the official state rock of California. The presence of serpentinite can indicate the presence of rare ecosystems because the high magnesium and low calcium content in its soil (serpentine soil) supports unique plant life.
Field identification & locations
Identified by its distinctive green color, waxy feel, and often 'scaly' or slickensided appearances. Common in orogenic belts and along faults. It feels slightly greasy or soapy to the touch.
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