metamorphic
Rounded green-gray pebble, likely serpentinite
Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite
AI-generated identification · may be incorrectUsually Mohs 2.5–5.5, waxy to greasy luster, green-gray to black mottling, fine-grained and massive; the pictured specimen may also be a chlorite-rich metamorphic pebble. Individual minerals and exact hardness cannot be confirmed from an image.
Identified More metamorphic →
Explore Rounded green-gray pebble, likely serpentinite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Usually Mohs 2.5–5.5, waxy to greasy luster, green-gray to black mottling, fine-grained and massive; the pictured specimen may also be a chlorite-rich metamorphic pebble. Individual minerals and exact hardness cannot be confirmed from an image.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during low-temperature metamorphism, commonly along faults and oceanic crust; most occurrences are Paleozoic to younger, depending on locality.
Uses & applications
Used as decorative stone, carvings, lapidary material, and historically as a source of asbestos-bearing rock; not generally used structurally because it can weather and contain chrysotile.
Geological facts
Serpentinite commonly contains magnetite, giving dark specks and occasional weak magnetism. Its smooth, rounded shape indicates transport by water or glacial action.
Field identification & locations
Look for a green waxy surface, low density, dark veining, and possible magnetism; a knife may scratch softer varieties. Common in California, the Appalachians, New Zealand, Italy, and ophiolite belts worldwide.
More like this
