metamorphic
Serpentinite
Serpentinite (composed primarily of minerals in the Serpentine group: Chrysotile, Lizardite, and Antigorite)
Hardness: 3-6 on the Mohs scale; Color: typically green, mottled green, or dark greenish-black; Luster: waxy, greasy, or silky; Crystal structure: monoclinic or orthorhombic (often appearing massive or fibrous); Cleavage: poor; Specific gravity: 2.5-2.6.
- Hardness
- 3-6 on the Mohs scale
- Color
- typically green, mottled green, or dark greenish-black
- Luster
- waxy, greasy, or silky
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Physical properties
Hardness: 3-6 on the Mohs scale; Color: typically green, mottled green, or dark greenish-black; Luster: waxy, greasy, or silky; Crystal structure: monoclinic or orthorhombic (often appearing massive or fibrous); Cleavage: poor; Specific gravity: 2.5-2.6.
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rocks (peridotite) from the Earth's mantle, typically at subduction zones or mid-ocean ridges through a process called serpentinization.
Uses & applications
Used as an architectural building stone (Verde Antique), for decorative carvings, as a source of asbestos (chrysotile), and in the production of magnesium fertilizers.
Geological facts
Serpentinite is the official state rock of California. It is unique because its formation involves the sequestration of large amounts of water into the rock's structure.
Field identification & locations
Identify in the field by its characteristic 'serpent-like' green mottled appearance and soapy or greasy feel. It is commonly found in ophiolite complexes, such as those in California, the Appalachian Mountains, the Swiss Alps, and New Zealand.
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