Streak is the colour of a mineral in powdered form and is a useful means of mineral identification. It is sometimes tested by rubbing a mineral on a piece of unglazed porcelain called a 'streak plate'. Laboratory tests are somewhat more complex since most gemstone minerals that need identification are harder than porcelian. A classic example of a streak test is with hematite. Although the mineral is gun-metal grey, in it's powdered form it is cherry red.