White Streak Plate
Streak Plates are used to help identify and classify rocks and minerals.
White Streak Plate measures 1 x 2"
How to use streak as an identification mark
A streak plate is an unglazed piece of porcelain
When testing for streak, the mineral must be crushed to determine the color of its powder. The color of the powder is the color of the streak. Instead of actually crushing a mineral to determine the streak, it is much simpler and cost-effective to swipe the mineral across a streak plate.
For minerals that are harder than the streak plate, this test cannot be used, since the mineral will remove tile material. This is rarely a problem, though; since most minerals where this test will be significant are softer than the streak plate (the streak plate has a hardness of about 6.5 on the Mohs scale).
Most mineral references don’t make a distinction between a white and colorless streak, since the difference is minimal. A mineral with a white or colorless streak will not leave a visible streak on a streak plate.
How to do it…
Swipe the mineral against the streak plate, but not hard enough to damage it.
The color of the powder that results on the streak plate is the streak color.