What is rubbing a mineral against a piece of unglazed ceramic tile a test for?

1 Answer
Martha W.
Jul 9, 2017

Streak.

Explanation:

Rubbing a mineral against a piece of unglazed ceramic tile is called the streak test. Streak shows the color of a mineral's powder. For example: Quartz, Amythest (purple), Rose Quartz (pink), Citrine (yellow) and Smokey quartz (tea colored to nearly black) are all quartz, so even though the look very different, they have the same streak.

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