Jade (Nephrite & Jadeite)
Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂ / NaAlSi₂O₆ · Monoclinic · also called nephrite, jadeite, greenstone, pounamu
Jade is two different minerals sharing one name and one property: an interlocking fibrous structure that makes them almost unbreakable. That toughness — not hardness — is why jade was carved into axes and blades long before it was carved into ornaments. Most 'jade' on sale is serpentine, dyed quartzite, or glass.
Properties
- Mohs hardness
- 6–7Nephrite 6–6.5; jadeite 6.5–7. Both are far tougher than their hardness suggests.
- Streak
- white
- Lustre
- greasy, vitreous
- Colour
- Green in many shades, but also white, lavender, black, and orange. Colour alone proves nothing.
- Cleavage
- No usable cleavage in the massive interlocking-fibre material.
- Fracture
- Splintery, and exceptionally tough
- Specific gravity
- 2.9–3.4 (water = 1)
- Magnetism
- Not magnetic
- Acid test
- No reaction
- UV
- Not fluorescent
Tests that confirm jade
- Extraordinarily tough. A knife will not scratch true jade, and it resists chipping in a way most stones do not.
- Cold to the touch and slow to warm in the hand.
- A dense, ringing tone when two pieces are tapped together, rather than a dull click.
What jade gets confused with
Each of these is settled by one test. Run that test first.
A steel knife marks serpentine but not jade. This one test resolves most cases.
Under a lens, dyed quartzite shows colour concentrated between visible grains.
Glass has bubbles, warms quickly in the hand, and chips conchoidally.
Where it is found
Serpentinite belts and subduction-zone metamorphic rocks. British Columbia, Myanmar, New Zealand, and Wyoming are major sources.
Is it worth anything?
Imperial jadeite is among the most expensive gem materials in the world. Nephrite is far more affordable. Treat any inexpensive 'jade' as a substitute until proven otherwise.