Color is least useful in identifying a mineral because the color can vary in each form of the mineral. The most useful way to identify a mineral is streak.
Minerals may be characterized and classified using unique physical properties such as hardness, luster, color, streak, specific gravity, cleavage, fracture, and tenacity.
Color is one of the physical properties of minerals and is considered when identifying minerals. However, color should not be used as a major characteristic of identifying mineral. Therefore, it is the least useful in identifying minerals as two minerals may have the same color.