The streak test: a simple way to narrow down an unknown mineral

The streak test is one of the easiest identification tools to add to a field kit because it only costs a couple of dollars. Drag the specimen across an unglazed porcelain tile (the back of a bathroom tile works if you do not want to buy a dedicated streak plate) and look at the color of the powder left behind, which is often different from the color of the specimen itself. Hematite is a great example, it can look black or silvery metallic but leaves a reddish brown streak every time. Pyrite leaves a greenish black to black streak. Magnetite leaves a black streak. Galena leaves a gray streak. The streak test only works on minerals softer than the porcelain itself (around 6 to 7 on the Mohs scale), anything harder will just scratch the plate instead of leaving a mark, which is itself useful information.