metamorphic
Serpentinite
Serpentinite (containing minerals of the Serpentine subgroup: Antigorite, Lizardite, and Chrysotile; formula (Mg,Fe)3Si2O5(OH)4)
Hardness: 2.5 to 5 on Mohs scale; Color: typically green (varying from olive to lime) with brownish or black inclusions; Luster: waxy to greasy; Crystal Structure: monoclinic; Cleavage: poor/irregular; Specific Gravity: 2.5 to 2.6.
- Hardness
- 2
- Luster
- waxy to greasy
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Physical properties
Hardness: 2.5 to 5 on Mohs scale; Color: typically green (varying from olive to lime) with brownish or black inclusions; Luster: waxy to greasy; Crystal Structure: monoclinic; Cleavage: poor/irregular; Specific Gravity: 2.5 to 2.6.
Formation & geological history
Formed via serpentinization, an exothermic reaction where ultrabasic rock from the Earth's mantle (peridotite) is hydrated at low temperatures in subduction zones or mid-ocean ridges. Specimens can date from various geological eras depending on tectonic history.
Uses & applications
Used as a decorative architectural stone (interiors), in some industrial asbestos contexts historically, for magnesium extraction, and as a popular carving stone for sculpture and jewelry.
Geological facts
Serpentinite is the state rock of California. It is unique because it often supports specialized flora (serpentine barrens) due to its high magnesium and low calcium content which can be toxic to most plants.
Field identification & locations
Identify by its waxy 'serpentine' feel and greenish color. It often shows a mottled appearance resembling snakeskin. Common in mountain ranges that were once ancient seafloors (e.g., California, Vermont, Italy, Greece).
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