metamorphic
Serpentine
Antigorite, Lizardite, or Chrysotile; formula generally (Mg,Fe)3Si2O5(OH)4
Hardness: 3-6 (Mohs scale), Color: Olive green to greenish-black, Luster: Waxy, greasy, or silky, Crystal structure: Monoclinic, Cleavage: Perfect, Specific gravity: 2.5-2.6
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Physical properties
Hardness: 3-6 (Mohs scale), Color: Olive green to greenish-black, Luster: Waxy, greasy, or silky, Crystal structure: Monoclinic, Cleavage: Perfect, Specific gravity: 2.5-2.6
Formation & geological history
Formed by the hydrothermal alteration of ultramafic rocks (like peridotite and pyroxenite) in oceanic crust and subduction zones; this process is called serpentinization.
Uses & applications
Used as a source of asbestos (chrysotile), decorative building stone (serpentine marble), and in jewelry/carvings (New Zealand Greenstone / Pounamu variants).
Geological facts
California designated serpentine as the first official state rock of any U.S. state in 1965. It is often associated with unique ecosystems because the soil derived from it is toxic to many plants.
Field identification & locations
Identified by its distinctive waxy feel, shades of green, and smooth, almost slippery surface. It is commonly found in mountain belts where oceanic crust has been uplifted, such as the Appalachian and Coast Ranges.
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