Malachite: the green of copper
A soft copper mineral that grows in rings like a tree, and has been a pigment, an ore and a carving stone for thousands of years.
Malachite forms where copper deposits meet air and water near the surface. Rainwater and groundwater break down copper ores, and the dissolved copper settles out again as green copper carbonate. It grows in thin layers over rounded, bubbly shapes, so a cut and polished face shows bands, rings and eyes in light and dark green.
Each band is a layer with a slightly different crystal size. Fine-grained layers look dark; coarser ones look light and silky. That is why no two polished pieces match, and why a good tumbled stone or bead shows crisp contrast between the bands.
Malachite often grows with azurite, its deep blue cousin. Both are copper carbonates, and azurite slowly changes into malachite over time when conditions shift. A specimen with both minerals shows the two stages side by side, which makes it a favourite with collectors and teachers.
For a shop, the main thing to know is that malachite is soft. At 3.5 to 4 on the Mohs scale it scratches against quartz, dislikes acids and should never go in water for drinking. Sold polished and kept dry, it is a durable and very popular stone.
Every band is a layer of copper that settled out of water. No two pieces share a pattern.
