The color of the specimen as it appears to the naked eye under normal lighting conditions. Some mineral as gold will only appear as one color, but due to contaminants and crystal light distortion, many minerals could appear in multiple colors.
The streak is the coloration of a mineral in the form of a powder. Luster refers to the absorption, mirror image, or refraction of light by the surface of the mineral. Minerals have various lusters that are somewhat self-explanatory such as dull, earthy, metallic, silky, pearly, and resinous — also magnetism.
Certain materials exhibit magnetism or an attraction to a magnet, and some will display this property only when heated. Minerals possess physical properties which aid in identification.