metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4)
Hardness: 3 to 6 on Mohs scale; Color: Dark green to black with lighter green mottling; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic; Specific Gravity: 2.5 to 2.8.
- Hardness
- 3 to 6 on Mohs scale
- Color
- Dark green to black with lighter green mottling
- Luster
- Waxy, greasy, or silky
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Physical properties
Hardness: 3 to 6 on Mohs scale; Color: Dark green to black with lighter green mottling; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic; Specific Gravity: 2.5 to 2.8.
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rocks (like peridotite) from the Earth's mantle. This process, called serpentinization, typically occurs at tectonic plate boundaries.
Uses & applications
Used as decorative stone in architecture, for carvings (soapstone varieties), and historically as a source of asbestos. High-quality specimens are used in jewelry and lapidary arts.
Geological facts
Serpentinite is the official state rock of California. It often hosts rare minerals and is associated with 'serpentine barrens' where the unique soil chemistry limits plant growth to specialized species.
Field identification & locations
Identify by its characteristic 'snake-skin' appearance, waxy feel, and green-mottled color. Commonly found in ophiolite belts and subduction zones (e.g., California, Mediterranean, Alps). Collectors look for smooth, well-patterned river-tumbled stones.
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