metamorphic

Tumbled greenstone (likely serpentine or jade-like stone)

Likely serpentine-rich serpentinite; exact identification is not possible from the image alone

AI-generated identification · may be incorrect

Dark green, opaque, smooth and rounded with a subdued polished luster. Serpentine has Mohs hardness 2.5–5.5; serpentinite is typically fine-grained and lacks visible cleavage.

Identified September 27, 2026More metamorphic →

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Physical properties

Dark green, opaque, smooth and rounded with a subdued polished luster. Serpentine has Mohs hardness 2.5–5.5; serpentinite is typically fine-grained and lacks visible cleavage.

Formation & geological history

Serpentinite forms when water alters ultramafic rocks, commonly in ancient oceanic crust and along tectonic plate boundaries. The specimen has been mechanically tumbled; its geological age cannot be determined from the photo.

Uses & applications

Tumbled stones are used for collecting, crafts, and inexpensive jewelry. Serpentinite is also used as decorative stone and, in some regions, as building material.

Geological facts

The appearance could also match other dark-green stones, including nephrite or green jasper; a photo cannot reliably distinguish them.

Field identification & locations

Look for a dense, waxy-to-dull surface and green mottling; hardness and mineral tests are needed for confirmation. Serpentinite occurs in many mountain belts, including California, Italy, and New Zealand.