metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 (Mohs), Color: Mottled shades of green, black, and greenish-gray; Luster: Waxy to greasy; Crystal Structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.5-2.8
- Color
- Mottled shades of green, black, and greenish-gray
- Luster
- Waxy to greasy
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Physical properties
Hardness: 3-6 (Mohs), Color: Mottled shades of green, black, and greenish-gray; Luster: Waxy to greasy; Crystal Structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.5-2.8
Formation & geological history
Formed through 'serpentinization,' a low-temperature metamorphic process where mafic/ultramafic rocks from the Earth's mantle are hydrated by water at tectonic plate boundaries. Common in ophiolite complexes.
Uses & applications
Used as decorative architectural stone, in making 'green marble' countertops, figurines, and historically as a source of asbestos or magnesium minerals.
Geological facts
Serpentinite is the state rock of California. It can contain small amounts of magnetite which may make it slightly magnetic, and it often creates unique soil conditions that lead to specialized plant biodiversity.
Field identification & locations
Identify in the field by its dark green, mottled 'snakeskin' appearance, waxy feel, and relatively low hardness compared to jade. Often found along fault zones or in coastal mountain ranges.
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