Serpentine
(Mg,Fe)₃Si₂O₅(OH)₄ · Monoclinic · also called antigorite, chrysotile, new jade
Serpentine forms when water alters magnesium-rich igneous rock, and it is very often sold as jade. It is much softer than real jade, and a steel knife will mark it where nephrite resists. Treat fibrous serpentine with care and do not cut or grind it dry.
Properties
- Mohs hardness
- 3–5Variable — fibrous chrysotile is soft, massive antigorite is considerably harder.
- Streak
- white
- Lustre
- greasy, waxy, silky
- Colour
- Green in every shade, often mottled or veined with darker green and black.
- Cleavage
- Massive varieties show no cleavage.
- Fracture
- Conchoidal to splintery
- Specific gravity
- 2.5–2.6 (water = 1)
- Magnetism
- Not magnetic
- Acid test
- No reaction
- UV
- Not fluorescent
Tests that confirm serpentine
- Greasy, almost soapy surface feel, with a waxy sheen.
- Mottled green colouring that genuinely resembles snakeskin — the origin of the name.
- Fibrous varieties should not be crushed or sanded; chrysotile is a form of asbestos.
What serpentine gets confused with
Each of these is settled by one test. Run that test first.
Jade is harder (6–6.5) and exceptionally tough; a knife will not scratch it, but it marks serpentine.
Chlorite peels into flakes; serpentine is massive.
Where it is found
Serpentinite belts along old tectonic boundaries — California, Cyprus, the Alps, and Newfoundland among many.
Is it worth anything?
Low. Frequently mislabelled 'new jade', 'Korean jade', or 'olive jade' — all of which are serpentine, not jade.