What Does Streak Tell You About a Mineral?

What Does Streak Tell YouGeologists 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. How do you get a powdered form? Simple. Geologists uses streak plates to powder the mineral to test the streak.

A streak plate is a piece of unglazed porcelain tile. When you rub the mineral sample on the plate, the powder will stay on the tile. Some minerals have a streak color that is the same as their outward color, while others have a streak color that is totally different. For example, azurite has a blue outward color and a blue streak and limonite is a yellow-brown color both outside and in powder form. Conversely, yellow sulfur has a white streak while gray hematite has a cherry red streak color.

For details on how to perform the streak test with your own samples and testing plates, you can read this article in the Dig Into Geology of our website.

 

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