metamorphic
Serpentine (likely antigorite-rich serpentinite)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with possible magnetite, chromite, or talc
AI-generated identification · may be incorrectDark green to black, mottled and waxy-to-greasy luster with pale veining; typically massive, fine-grained, and lacking visible cleavage. Hardness is about 2.5–4 Mohs; specific gravity approximately 2.5–2.6.
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Physical properties
Dark green to black, mottled and waxy-to-greasy luster with pale veining; typically massive, fine-grained, and lacking visible cleavage. Hardness is about 2.5–4 Mohs; specific gravity approximately 2.5–2.6.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrothermally altered by water, commonly in oceanic crust and subduction zones. Most specimens are Paleozoic to Cenozoic, depending on their tectonic setting.
Uses & applications
Used as decorative stone, carvings, ornamental objects, and historically for countertops and architectural material; prized varieties may be cabochon-cut. Dust from some serpentinite can contain asbestos-form minerals, so avoid inhalation when cutting.
Geological facts
Its characteristic green color results from hydration and alteration of magnesium-rich minerals. It may be confused with jade, but is generally softer and less tough.
Field identification & locations
Identify by its green-black mottling, waxy surface, low hardness, and often fibrous or veined texture; common in California, Italy, New Zealand, Canada, and tectonically active belts worldwide.
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