When a mineral's color is the result of the elements present, color can be a useful aid for identification. For example, malachite is always green, and gold is always yellow. Most native elements and sulphides have distinctive colors. However, trying to determine what a specimen is by color alone can be misleading. Impurities and defects in crystal structure can change the color of a mineral.
Pure quartz is clear, but it can occur in white, pink, blue, purple, green, and yellow forms.
Also, colors can change as minerals are exposed to weathering and erosion. For this reason, always examine a freshly broken surface when evaluating color. In general, most minerals cannot be identified by color alone. A useful identifying characteristic is the way in which light reflects off the surface of a mineral, called its luster. For example, native metals, most sulphides, and some oxides have a metallic luster.