metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals: (Mg,Fe)3Si2O5(OH)4)
Hardness: 3-6 (variable); Color: Dark green to greenish-blue with black mottling; Luster: Greasy, waxy, or dull; Structure: Often fibrous or massive; Cleavage: Poor.
- Hardness
- 3-6 (variable)
- Color
- Dark green to greenish-blue with black mottling
- Luster
- Greasy, waxy, or dull
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Physical properties
Hardness: 3-6 (variable); Color: Dark green to greenish-blue with black mottling; Luster: Greasy, waxy, or dull; Structure: Often fibrous or massive; Cleavage: Poor.
Formation & geological history
Forms through the hydrothermal metamorphism (serpentinization) of ultramafic rocks like peridotite from the Earth's mantle, typically at tectonic plate boundaries or mid-ocean ridges.
Uses & applications
Used as decorative architectural stone, a source of magnesium, and historically as a source of asbestos. Used in jewelry as 'New Jade' and for carvings.
Geological facts
It is the official state rock of California. The name comes from its resemblance to the skin of a serpent. It often marks the presence of ancient seafloor that has been pushed onto land.
Field identification & locations
Identifiable by its characteristic green color and 'soapy' or greasy feel. Often found in ophiolite complexes. Collectors should be aware that some fibrous varieties contain asbestos.
