metamorphic
Tumbled greenstone (likely serpentinite or nephrite)
Serpentinite: Mg-rich serpentine minerals; possible nephrite: tremolite–actinolite amphibole
AI-generated identification · may be incorrectOlive-green, fine-grained, rounded and polished with a waxy to faintly greasy luster; typically Mohs 2.5–4 for serpentinite or 6–6.5 for nephrite. No visible cleavage; compact massive texture and moderate-to-high density.
Identified More metamorphic →
Explore Tumbled greenstone (likely serpentinite or nephrite) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Olive-green, fine-grained, rounded and polished with a waxy to faintly greasy luster; typically Mohs 2.5–4 for serpentinite or 6–6.5 for nephrite. No visible cleavage; compact massive texture and moderate-to-high density.
Formation & geological history
Formed when ultramafic mantle rocks were hydrated during metamorphism, commonly in oceanic crust or subduction zones; ages vary widely from Precambrian to modern tectonic belts. The pictured piece is tumbled, obscuring diagnostic textures.
Uses & applications
Used for carvings, beads, ornamental stone, and sometimes landscaping; true nephrite has jewelry and carving value, while common serpentinite is inexpensive.
Geological facts
Green color commonly comes from serpentine, chlorite, magnetite, or amphibole minerals. A steel scratch test can help distinguish softer serpentinite from harder nephrite, though it may damage the specimen.
Field identification & locations
Common in California, New Zealand, Canada, Russia, Italy, and Alpine ophiolite belts. Confirm with hardness, density, streak, and ideally petrographic or laboratory testing; visual identification alone is uncertain.
More like this
