Hematite has an interesting quality of leaving a red mark when scraped on something, even though it is a black stone. Because of this, it gets its name from the greek haima, meaning blood.

Grinding hematite makes red ochre, a pigment and abrasive.

Paraphrased from The Complete Metalsmiths Handbook by TimMcCreight.
Thanks to Gritchka for a correction about the origen of haima