metamorphic
Serpentinite
Serpentinite (composed largely of Serpentine minerals such as Lizardite, Antigorite, and Chrysotile: Mg3Si2O5(OH)4)
Hardness: 2.5 to 5 on Mohs scale; Color: Shades of green, yellowish-green to black; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific gravity: 2.5 to 2.6.
- Hardness
- 2
- Color
- Shades of green, yellowish-green to black
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 2.5 to 5 on Mohs scale; Color: Shades of green, yellowish-green to black; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific gravity: 2.5 to 2.6.
Formation & geological history
Formed through the hydration of ultramafic rocks (like peridotite) from the Earth's mantle, a process called serpentinization. This typically occurs at tectonic plate boundaries and subduction zones.
Uses & applications
Used as decorative stone in architecture, for carvings and sculptures, and historically as a source of asbestos. High-quality translucent varieties are used in jewelry as 'New Jade'.
Geological facts
Serpentinite is the official state rock of California. It can contain magnetite, making some specimens slightly magnetic, and may contain trace elements like nickel and chromium.
Field identification & locations
Identify by its characteristic 'snake-skin' appearance, waxy feel, and green color. To distinguish from jade, note that it is significantly softer. Common in mountain belts and ophiolite complexes.
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