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

Our readers have some amazing questions and this week is no exception. In fact, this is a very popular question about cleaning your 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.

There are a couple of things that you can do to clean the streak plates. For some of them, you can soak them in warm soapy water for a few minutes then use a kitchen sponge to scrub the surface. This works pretty well to remove the powder of some of the softer minerals. Now a streak plate is about a seven on the Mohs Hardness scale so any mineral that is a seven or higher on the scale will not show a streak because they are harder than the plate. However, these harder minerals will scratch the surface of the plate making them harder to clean because mineral powder gets ground into the porcelain.

For plates that are older and scratched you can use this handy scrubber called the Magic Eraser. These are made by Mr. Clean and you just get them wet and then rub them over the streak plate and they come clean. Over time the plates will get scratched and stained to the point where even the magic eraser won’t work and you will need to replace them but routinely cleaning you streak plates will help keep them nice for many uses.

Remember to keep your questions coming in through the dig into geology section on our website or email us at  Please comment below and subscribe to our channel so that you get the next installment of ask a geologist.  Until next time, rock on everybody.

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