Streak test
The streak test means rubbing a rock on the back of a ceramic tile to see the colour of its powder.
When you scrape a mineral across a rough, unglazed piece of ceramic, such as the back of a bathroom tile, it leaves a line of fine powder called a streak. The streak colour can be different from the colour of the rock itself, and it is a handy way to tell some minerals apart.
This test is great for spotting meteorwrongs, which are Earth rocks mistaken for meteorites. Hematite, a common iron mineral, leaves a reddish-brown streak, even when the rock looks black or silver. Magnetite, another iron mineral that sticks to magnets, leaves a black streak. Most stony meteorites, such as ordinary chondrites, leave little or only a pale grey streak, although a rusty, weathered meteorite may leave a brownish one. So if a dark, heavy rock leaves a strong red-brown or black line, it is probably not a meteorite.
The streak test only works on part of the rock, so pick a corner where a small mark does not matter, and always ask permission first, because rubbing scratches a little away. Never lick or taste a rock to see its colour better, and ask an adult before testing anything you find.
Related terms
Level: Beginner Ages 7 and up