metamorphic
Serpentinite
Serpentinite (composed mainly of Group: Serpentine; (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4)
Hardness: 3 to 6 on Mohs scale; Color: Green, yellowish-green, or grayish-green with mottled streaks; Luster: Greasy, waxy, or silky; Crystal Structure: Monoclinic; Cleavage: Poor or basal; Specific Gravity: 2.5 to 3.2.
- Hardness
- 3 to 6 on Mohs scale
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3 to 6 on Mohs scale; Color: Green, yellowish-green, or grayish-green with mottled streaks; Luster: Greasy, waxy, or silky; Crystal Structure: Monoclinic; Cleavage: Poor or basal; Specific Gravity: 2.5 to 3.2.
Formation & geological history
Formed through the process of serpentinization, which is the hydration of ultramafic rocks (like peridotite) from the Earth\'s mantle. This typically occurs at tectonic plate boundaries and subduction zones through low-temperature metamorphism.
Uses & applications
Used as a decorative architectural stone, a source of magnesium, and historically as a source of asbestos. High-quality varieties like bowenite are used for carvings and jewelry.
Geological facts
Serpentinite is the official state rock of California. It often contains 'slickensides,' which are polished, grooved surfaces caused by movement along fault planes during its formation.
Field identification & locations
Identify in the field by its distinctive 'serpent-like' green mottled appearance and slick, soapy feel. It is commonly found in ophiolite complexes and mountain belts like the Coast Ranges of California or the Appalachian Mountains.
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