metamorphic
Tumbled greenstone (likely serpentinite or altered basalt)
Serpentinite, predominantly serpentine-group minerals; exact identification requires testing
AI-generated identification · may be incorrectUsually Mohs 2.5–4, opaque green to gray-green, waxy to dull luster, fine-grained and massive with irregular dark veining. The rounded shape indicates natural abrasion or tumbling; composition cannot be confirmed visually.
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Physical properties
Usually Mohs 2.5–4, opaque green to gray-green, waxy to dull luster, fine-grained and massive with irregular dark veining. The rounded shape indicates natural abrasion or tumbling; composition cannot be confirmed visually.
Formation & geological history
Serpentinite forms when ultramafic mantle rocks hydrate during hydrothermal alteration, commonly in ophiolites and subduction zones; its age varies widely from Precambrian to Recent tectonic settings. If instead basaltic, it may be an altered mafic volcanic rock.
Uses & applications
Used as a decorative or lapidary stone, carvings, beads, and occasionally architectural stone; this specimen appears mainly collectible or ornamental.
Geological facts
Green color and black veining are characteristic of serpentine-rich rocks, but similar appearances occur in chlorite-rich basalt, nephrite-like rocks, and jade substitutes. It is not identifiable as true jade from appearance alone.
Field identification & locations
Common sources include California, New Zealand, Italy, Canada, and serpentinite belts worldwide; check for a waxy feel, low hardness, and possible white streak, and avoid acid-based conclusions. A hardness, streak, density, and microscopic or Raman/XRF test would improve identification.
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