metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine minerals: Mg3Si2O5(OH)4)
Hardness: 3-6 on Mohs scale; Color: typically dark green to grayish-black with mottled patterns; Luster: waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: poor/conchoidal fracture; Specific Gravity: 2.2-2.9
- Hardness
- 3-6 on Mohs scale
- Color
- typically dark green to grayish-black with mottled patterns
- Luster
- waxy, greasy, or silky
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Physical properties
Hardness: 3-6 on Mohs scale; Color: typically dark green to grayish-black with mottled patterns; Luster: waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: poor/conchoidal fracture; Specific Gravity: 2.2-2.9
Formation & geological history
Formed through the hydrothermal metamorphism (serpentinization) of mafic and ultramafic rocks from the Earth's mantle, such as peridotite. This most commonly occurs at tectonic plate boundaries or mid-ocean ridges.
Uses & applications
Used as decorative architectural stone, carvings, and historically as a source of asbestos. High-quality varieties are used in lapidary art and jewelry.
Geological facts
Serpentinite is the official state rock of California. It often creates 'serpentine barrens,' which are unique ecosystems where only specific heavy-metal-tolerant plants can grow due to the rock's chemistry.
Field identification & locations
Identify in the field by its distinctive 'snake-skin' appearance, greenish hue, and smooth, waxy feel. It is commonly found in ophiolite complexes and subduction zones worldwide.
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