Malachite forms in the upper, oxidized parts of copper deposits and commonly has a botryoidal habit. The intense green color is typical of copper (although chromium, nickel and iron also account for green mineral colors). It bubbles with cold acid, showing malachite to be a carbonate.
You'll usually see malachite in rock shops and in ornamental objects, where its strong color and concentric banded structure produce a very picturesque effect. This specimen shows a more massive habit than the typical botryoidal habit that mineral collectors and carvers fancy. Malachite never forms crystals of any size.
The blue mineral azurite, Cu3(CO3)2(OH)2, commonly accompanies malachite.