Serpentinite

Rock of serpentine minerals, formed when mantle rock reacts with seawater. Slick, green and mottled.

Serpentinite specimen — Photo: Gabriel HM, CC BY-SA 4.0, via Wikimedia Commons

How to identify serpentinite

Green to black with a waxy, slippery look.
Polished, scaly surfaces where it was sheared.
Softer than it looks.

Often confused with

Serpentine
Serpentine is the mineral; serpentinite is the rock.
Compare side by side
Nephrite
Nephrite is much tougher and harder.
Compare side by side

Where it's found

California Coast Ranges
Newfoundland
Thessaly, Greece

Uses

Decorative stone ('verde antique').

Rock tumbling

Can be tumbled with care.

Did you know?

Serpentinite is California's official state rock.

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