igneous
Rounded green-gray pebble, likely serpentinite or altered basalt
Probable serpentinite (hydrated ultramafic rock) or greenstone; image insufficient for certain identification
AI-generated identification · may be incorrectFine-grained, smooth water-worn surface; pale green-gray color with dull to weakly waxy luster and small pits. Estimated Mohs hardness 3–6 depending on composition; no visible crystals or cleavage.
Identified More igneous →
Explore Rounded green-gray pebble, likely serpentinite or altered basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Fine-grained, smooth water-worn surface; pale green-gray color with dull to weakly waxy luster and small pits. Estimated Mohs hardness 3–6 depending on composition; no visible crystals or cleavage.
Formation & geological history
Likely naturally weathered and rounded by stream, beach, or glacial transport. If serpentinite, it formed when mantle peridotite was hydrothermally altered, commonly during ancient oceanic or tectonic processes.
Uses & applications
Usually collected as a curiosity or used as a decorative pebble; serpentinite may be carved or used as ornamental stone, while basaltic pebbles have limited construction value.
Geological facts
The green color may come from serpentine minerals, chlorite, epidote, or altered mafic minerals. A hardness test, streak test, and examination of a fresh surface would distinguish serpentinite from basalt, greenstone, or slag.
Field identification & locations
Common in areas with ultramafic rocks or volcanic/mafic terrains, including California, Italy, New Zealand, and many glacial or coastal deposits. Check for a waxy feel, dark green veins, magnetism, and white streak; avoid assuming identity from color alone.
