metamorphic
Greenstone / Serpentinite
Serpentinite (composed primarily of serpentine minerals: Mg3Si2O5(OH)4)
Hardness: 2.5 to 5 on Mohs scale; Color: Sage green, dark forest green, often mottled; Luster: Waxy, greasy, or dull; Structure: Microcrystalline, often showing foliation or shearing; Cleavage: Often fibrous or splintery.
- Hardness
- 2
- Color
- Sage green, dark forest green, often mottled
- Luster
- Waxy, greasy, or dull
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Physical properties
Hardness: 2.5 to 5 on Mohs scale; Color: Sage green, dark forest green, often mottled; Luster: Waxy, greasy, or dull; Structure: Microcrystalline, often showing foliation or shearing; Cleavage: Often fibrous or splintery.
Formation & geological history
Formed by the hydration and metamorphic transformation of ultramafic rock (like peridotite) from the Earth’s mantle at low temperatures and high pressures, typically at tectonic plate boundaries.
Uses & applications
Used as decorative building stone, in sculptures (steatite variants), and historically as a source for magnesium. Some varieties are used in jewelry as 'New Zealand Jade' or Bowenite.
Geological facts
Serpentinite is the official state rock of California. It is often associated with specific 'serpentine soils' that are toxic to many plants but host rare, endemic species.
Field identification & locations
Identify by its characteristic 'serpent-like' green color and slightly waxy feel. It is commonly found in ophiolite complexes and subduction zones where oceanic crust has been uplifted.
