metamorphic
Serpentinite
Serpentinite (composed largely of serpentine group minerals including Antigorite, Lizardite, or Chrysotile)
Hardness: 3-6 (Mohs scale); Color: green, greenish-grey, or black; Luster: waxy, greasy, or silky; Crystal structure: Monoclinic; Cleavage: poor; Specific gravity: 2.2–2.9.
- Hardness
- 3-6 (Mohs scale)
- Color
- green, greenish-grey, or black
- Luster
- waxy, greasy, or silky
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Physical properties
Hardness: 3-6 (Mohs scale); Color: green, greenish-grey, or black; Luster: waxy, greasy, or silky; Crystal structure: Monoclinic; Cleavage: poor; Specific gravity: 2.2–2.9.
Formation & geological history
Formed through serpentinization, a low-temperature metamorphic process where ultramafic rocks (like peridotite from the Earth's mantle) are hydrated by water at tectonic boundaries (subduction zones or mid-ocean ridges).
Uses & applications
Used as decorative architectural stone, a source of magnesium, historically as a source of asbestos, and in specialized carvings and jewelry (often called 'New Zealand Greenstone' or 'Jade' variants).
Geological facts
Serpentinite is the official state rock of California. It is unique for its chemistry, which creates 'serpentine soils' that are toxic to many plants but host rare, endemic species.
Field identification & locations
Identify in the field by its distinctive 'snake-skin' appearance, waxy feel, and green hue. It is commonly found in ophiolite complexes where ancient seafloor has been pushed onto continental crust.
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