metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals like Antigorite, Lizardite, and Chrysotile)
Hardness: 3-6 on Mohs scale; Color: Greenish-yellow to dark green with dark mottled patches; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.2-2.9
- Hardness
- 3-6 on Mohs scale
- Color
- Greenish-yellow to dark green with dark mottled patches
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3-6 on Mohs scale; Color: Greenish-yellow to dark green with dark mottled patches; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.2-2.9
Formation & geological history
Formed through serpentinization, a low-temperature metamorphic process where ultramafic rocks (like peridotite) from the Earth's mantle are hydrated by water. Common in plate boundary zones and ophiolites.
Uses & applications
Used as decorative architectural stone, source of magnesium, and historically as a source of asbestos. High-quality varieties are used for carvings and jewelry known as 'New Jade'.
Geological facts
It is the official state rock of California. The dark spots often visible are typically magnetite or chromite crystals that formed during the metamorphic process.
Field identification & locations
Identify by its characteristic 'serpent-like' green mottled appearance and waxy feel. It is commonly found in mountain belts where oceanic crust has been uplifted, such as the Appalachian or Coast Ranges.
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