Malachite
Cu₂CO₃(OH)₂ · Monoclinic
Malachite is the green weathering product of copper ore and one of the most visually distinctive minerals there is. The concentric banding in polished slabs is unlike anything else. Handle raw material with reasonable care and wash your hands — it is a copper compound.
Properties
- Mohs hardness
- 3.5–4
- Streak
- pale green
- Lustre
- silky, dull, vitreous
- Colour
- An intense, unmistakable green, usually in concentric light and dark bands when cut or broken.
- Cleavage
- Perfect in one direction, rarely visible in the botryoidal masses normally found.
- Fracture
- Fibrous, splintery
- Specific gravity
- 3.6–4 (water = 1)
- Magnetism
- Not magnetic
- Acid test
- Fizzes on contact
- UV
- Not fluorescent
Tests that confirm malachite
- Fizzes in dilute acid — it is a carbonate, which surprises people who expect a copper mineral to be inert.
- Pale green streak.
- Banded, botryoidal, grape-like masses with a silky fibrous interior.
What malachite gets confused with
Each of these is settled by one test. Run that test first.
Chrysocolla
Chrysocolla is bluer, softer, and does not fizz in acid.
Dyed howlite or magnesite
Dyed imitations show colour concentrated in cracks and lack malachite's fine concentric banding.
Where it is found
The oxidised upper zones of copper deposits, very often with blue azurite.
Is it worth anything?
Common as polished slabs and tumbled stones. Fine crystal specimens and large banded pieces from the Congo command real prices.