metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 (Mohs); Color: Green, yellow, or blue-green with mottling; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: Often fibrous or platy; Specific Gravity: 2.2-2.9
- Hardness
- 3-6 (Mohs)
- Color
- Green, yellow, or blue-green with mottling
- Luster
- Waxy, greasy, or silky
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Physical properties
Hardness: 3-6 (Mohs); Color: Green, yellow, or blue-green with mottling; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: Often fibrous or platy; Specific Gravity: 2.2-2.9
Formation & geological history
Formed by the hydration of ultramafic rocks (like peridotite) from the Earth's mantle through a process called serpentinization, typically at tectonic plate boundaries/subduction zones.
Uses & applications
Used as a decorative stone in architecture, for internal cladding, and historically as a source of asbestos. High-quality varieties like bowenite are used for jewelry or carvings.
Geological facts
It is the state rock of California and is often referred to as 'greenstone'. It can sometimes contain trace amounts of magnetite, making it slightly magnetic.
Field identification & locations
Identify in the field by its distinctive 'snake-skin' appearance, waxy feel, and green hue. Common in ophiolite complexes and fault zones. Collectors look for translucent or unusually colored specimens.
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