Did any of the minerals you investigated have a streak color that is different from the mineral color?
Answers
Answer:
Explanation:
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 to swipe the mineral across a streak plate. A streak plate is an unglazed piece of porcelain, such as the underside of a ceramic tile. This is the most popular method of streak testing, since the color of the streak plate is white, the color of the mineral trace is easy to see. 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 an average hardness of about 6½ 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.