metamorphic
Serpentinite
Serpentinite (composed largely of serpentine group minerals including antigorite, lizardite, and chrysotile)
Hardness: 2.5 to 5 on Mohs scale; Color: Variable shades of green to black, often mottled or waxy; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Often fibrous or platy.
- Hardness
- 2
- Color
- Variable shades of green to black, often mottled or waxy
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 2.5 to 5 on Mohs scale; Color: Variable shades of green to black, often mottled or waxy; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Often fibrous or platy.
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rocks (like peridotite) from the Earth’s mantle, a process called serpentinization occurring at low temperatures and high pressures, often at tectonic plate boundaries or mid-ocean ridges.
Uses & applications
Used as a source of asbestos (historically), decorative building stone, carvings, and sometimes as a host rock for minerals like jadeite, chromite, and platinum group elements.
Geological facts
Serpentinite is the state rock of California. It often creates 'serpentine barrens', which are unique ecosystems where the soil chemistry is toxic to many plants but supports rare, specialized flora.
Field identification & locations
Identify by its characteristic waxy 'snake-skin' appearance, greasy feel, and variations of dark green color. It is commonly found in ophiolite complexes and subduction zones. Collectors should look for unique banding or chatoyant fibers.
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