metamorphic
Greenstone / Serpentinite
Serpentinite (composed primarily of minerals from the serpentine group Mg3Si2O5(OH)4)
Hardness: 2.5–6.0 (variable); Color: Mottled green, dark grey, and white; Luster: Greasy to waxy or dull; Crystal Structure: Microcrystalline; Cleavage: Poorly defined or massive; Specific Gravity: 2.5–2.6.
- Hardness
- 2
- Color
- Mottled green, dark grey, and white
- Luster
- Greasy to waxy or dull
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 2.5–6.0 (variable); Color: Mottled green, dark grey, and white; Luster: Greasy to waxy or dull; Crystal Structure: Microcrystalline; Cleavage: Poorly defined or massive; Specific Gravity: 2.5–2.6.
Formation & geological history
Formed from the hydrothermal alteration (serpentinization) of mafic or ultramafic silicate rocks, typically at tectonic plate boundaries or oceanic crust. Often dates from Precambrian to Cenozoic eras.
Uses & applications
Used for architectural cladding, decorative carvings, or as a source of asbestos (historically). High-quality pieces are used in jewelry as 'New Zealand Jade' (Greenstone) or lapidary art.
Geological facts
Serpentinite is the state rock of California. It often contains inclusions of quartz or calcite, creating the white veining seen in this specimen. It can be associated with rare minerals like chromite or magnetite.
Field identification & locations
Identify by its waxy 'soapy' feel and mottled green coloring. Frequently found in ophiolite belts (exposed ancient seafloor). Collectors should look for smoothness and translucency at the edges.
More like this
