The streak test is valuable because many minerals occur in a variety of apparent colors – but all specimens of that mineral share a similar streak color. For example: specimens of hematite can be black, red, brown, or silver in color and occur in a wide variety of habits; however, all specimens of hematite produce a streak with a reddish color. This is a valuable test for hematite. It can be used to differentiate hematite from a large number of other opaque minerals with a high specific gravity and similar color and habit.

Fluorite is another mineral where the apparent color can be different from the color of the streak. Specimens of fluorite can be green, yellow, purple, blue, or colorless. However, all specimens of fluorite have a white streak. Specimens of pyrite always have a brassy yellow color; however, all specimens of pyrite produce a black streak.