Streak is the color of a mineral when it is crushed to a powder. The easiest way to determine a mineral’s streak is to rub the edge of a specimen against an unglazed porcelain tile. Minerals with a hardness less than 7 will leave a streak. For many the streak will be white, so always look carefully. Minerals harder than 7 will not leave a streak and might even scratch the streak plate itself.
To learn more about mineral streak click on the streak graphic on the right.