This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American Talc - Gypsum - Calcite - Fluorite - Apatite ...
The hardness scale was created by trying to scratch one mineral with another. It was then recorded which mineral left a scratch. For example, Corundum, (Ruby and Sapphire) was used to scratch Apatite.
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