metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals, Mg3Si2O5(OH)4)
Hardness: 3-6 (Mohs); Color: Mottled green, dark green, to blackish; Luster: Waxy to greasy; Crystal Structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.5-3.2
- Hardness
- 3-6 (Mohs)
- Color
- Mottled green, dark green, to blackish
- Luster
- Waxy to greasy
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Physical properties
Hardness: 3-6 (Mohs); Color: Mottled green, dark green, to blackish; Luster: Waxy to greasy; Crystal Structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.5-3.2
Formation & geological history
Formed through the hydration of ultramafic rocks (like peridotite) from the Earth's mantle, a process called serpentinization, typically at tectonic plate boundaries.
Uses & applications
Used as decorative stone, in construction as 'green marble', and historically as a source of asbestos. High-quality specimens are used in jewelry and carvings.
Geological facts
Serpentinite is the state rock of California. It often creates unique ecosystems because the soil derived from it is high in heavy metals and low in essential plant nutrients.
Field identification & locations
Identify by its 'serpent-like' mottled green color, waxy feel, and the presence of slickensides (polished surfaces from tectonic movement). Commonly found in ophiolite complexes.
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