Ask-a-Geologist Q&A Video #12: How do you clean streak plates?

Several of our readers have written to us and asked: How do you clean streak plates? In case you are not familiar with streak plates, they are little pieces of unglazed porcelain tile that you use to test the streak color of a mineral. There are black streak plates and white streak plates. You use the black plates for light-colored minerals and white plates for dark-colored minerals. To test the streak, you rub the mineral across the streak plate and see what color shows up on the plate. That is the streak or the color of the mineral in powdered form. When you do the test you need to rub hard on the streak plate because you are trying to crush part of the sample into a fine powder. Over time the plates will become dirty and you will want to clean them.

Mineral Streak is an Important Test to Identify Samples

Geologists use many tests to determine the identity of a mineral. Streak can be one of the most important tests when trying to tell two similar minerals apart. A mineral’s streak is its color when the mineral in is powdered form.