What is this close-up picture? (WotsThat: Chalkboard dust)

Question

What object is shown in this zoomed-in close-up photo?

VanadiniteX · Accepted Answer

Chalkboard dust. Chalkboard dust is actually a mixture of calcium sulfate and other minerals that creates that distinctive white powder. Despite its common use in classrooms, chalk has been used for writing and art for thousands of years, with natural chalk deposits forming from ancient marine organisms.

Answer: Chalkboard dust

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