metamorphic
Serpentinite
Serpentinite (composed largely of serpentine group minerals including antigorite, lizardite, and chrysotile)
Hardness: 3-6 Mohs; Color: Dark green to black with mottled patterns; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific gravity: 2.5-3.2
- Hardness
- 3-6 Mohs
- Color
- Dark green to black with mottled patterns
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3-6 Mohs; Color: Dark green to black with mottled patterns; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific gravity: 2.5-3.2
Formation & geological history
Forms through the hydrothermal metamorphism of ultramafic rocks (like peridotite) from the Earth's mantle, typically at tectonic plate boundaries where water is introduced to the mantle wedge.
Uses & applications
Used as decorative architectural stone, for carvings, and historically as a source of asbestos. High-quality translucent varieties are used in jewelry as 'false jade'.
Geological facts
Serpentinite is the official state rock of California. It often creates unique soil chemistry that supports rare and endemic plant species that can tolerate high magnesium and heavy metals.
Field identification & locations
Identify by its 'snakeskin' appearance, greenish hue, and waxy feel. It is commonly found in ophiolite complexes along mountain belts and subduction zones.
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