metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine minerals: Mg3Si2O5(OH)4)
Hardness: 3-6 on Mohs scale; Color: typically green to dark green, often mottled; Luster: greasy, waxy, or silky; Crystal Structure: Monoclinic; Cleavage: poor; Specific Gravity: 2.5-3.2. It often feels slippery or 'soapy' to the touch.
- Hardness
- 3-6 on Mohs scale
- Color
- typically green to dark green, often mottled
- Luster
- greasy, waxy, or silky
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Physical properties
Hardness: 3-6 on Mohs scale; Color: typically green to dark green, often mottled; Luster: greasy, waxy, or silky; Crystal Structure: Monoclinic; Cleavage: poor; Specific Gravity: 2.5-3.2. It often feels slippery or 'soapy' to the touch.
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rocks (like peridotite) from the Earth’s mantle at relatively low temperatures. This process is called serpentinization and usually occurs at tectonic plate boundaries.
Uses & applications
Used as a decorative architectural stone (terrazzo, floor tiles), in jewelry (often as a jade simulant), and historically as a source of asbestos or for carvings. It is also the state rock of California.
Geological facts
Serpentinite can contain rare minerals and is known for creating 'serpentine barrens'—harsh soil environments where only specialized plants can grow due to high heavy metal content and low calcium.
Field identification & locations
Identify in the field by its distinct green color, waxy luster, and smooth, almost slippery surface. It is commonly found in ophiolite complexes and subduction zones in places like California, Vermont, the Alps, and New Zealand.
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