The same phenomenon that gives any object its color—the way its atoms interact with light. Certain atoms in minerals absorb some of the colors in visible light. You see the colors that are not absorbed. Minerals appear black when their atoms absorb all light, white when they absorb no light.
The great variety of atoms and atomic arrangements in minerals cause light to be absorbed differently—yielding a virtually limitless range of colors.

Colored By Copper: Blue and Green
These minerals come only in shades of blue or green. Why? They all contain copper. When atoms of copper combine with oxygen, as in the specimens here, the atoms absorb all colors from white light except blue and green—which reflect back to your eyes. Whether blue or green dominates in a mineral depends on how the copper atoms are placed in the structure.

Ancient Egyptians used malachite to make jewelry and eye shadow. Although relatively soft, it is an important ornamental stone nonetheless. The intricately patterned slab has been sliced and polished to a high gloss.