metamorphic
Tumbled dark green stone, likely serpentine or greenstone
Serpentinite (hydrated magnesium silicate minerals, chiefly antigorite/lizardite); possible chlorite-rich greenstone
AI-generated identification · may be incorrectSmooth, rounded, highly polished surface; dark olive-green to brown color with subtle mottling and waxy-to-greasy luster. Serpentine has Mohs hardness about 2.5–4, poor cleavage, and specific gravity around 2.5–2.6; exact identification requires testing.
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Physical properties
Smooth, rounded, highly polished surface; dark olive-green to brown color with subtle mottling and waxy-to-greasy luster. Serpentine has Mohs hardness about 2.5–4, poor cleavage, and specific gravity around 2.5–2.6; exact identification requires testing.
Formation & geological history
Serpentinite forms when ultramafic mantle rocks, such as peridotite, are hydrated during tectonic alteration, commonly in ophiolites and subduction zones. Its age depends on locality and may range from ancient Precambrian to modern tectonic settings.
Uses & applications
Used as a decorative stone, cabochon, carving material, and polished collectible; some serpentinite is quarried for architectural stone. Avoid cutting unknown material because fibrous asbestos minerals can occur in some serpentinites.
Geological facts
The intense polish and rounded shape indicate human tumbling, so original textures and diagnostic crystals are obscured. Similar-looking stones include nephrite jade, jasper, basalt, and slag.
Field identification & locations
Field clues include low hardness, green color, waxy luster, and possible dark veining; it may scratch with a steel knife. Confirm with hardness, streak, density, and microscopy—visual identification alone is uncertain.
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