metamorphic
Serpentine
Antigorite/Chrysotile/Lizardite (Mg,Fe)3Si2O5(OH)4
Hardness: 2.5-5.5 (Mohs scale); Color: green, yellow-green, or brownish-black; Luster: greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: perfect; Specific gravity: 2.5-2.6
- Hardness
- 2
- Color
- green, yellow-green, or brownish-black
- Luster
- greasy, waxy, or silky
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Physical properties
Hardness: 2.5-5.5 (Mohs scale); Color: green, yellow-green, or brownish-black; Luster: greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: perfect; Specific gravity: 2.5-2.6
Formation & geological history
Formed by the low-temperature hydrothermal alteration and metamorphism of ultramafic rocks (peridotite) from the Earth's mantle, a process known as serpentinization. Typically found in ophiolite complexes along convergent plate boundaries.
Uses & applications
Used as a source of asbestos, decorative building stone, carvings, gemstones (Williamsite variety), and historically in industrial fireproofing.
Geological facts
Serpentine is the state rock of California. Its name is derived from the Latin 'serpentinus' because of its resemblance to the skin of a snake. It can sometimes contain magnetic inclusions like magnetite.
Field identification & locations
Identified by its distinctive waxy sheen and greasy feel. Look for it in tectonic subduction zones like the Pacific Coast of North America or the Alps. It is often fibrous or platy and can be easily scratched by a steel knife if the hardness is low.
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