the.com/stibnite

means Stibnite is a soft, lead-gray mineral of antimony sulfide, often forming long, glittering, blade-like crystals, historically ground up and used as eye cosmetic and as the chief ore of antimony.

from The name comes from the Latin 'stibium,' the old word for antimony, which is also why antimony's chemical symbol is 'Sb.' That Latin term traces back through Greek 'stibi' or 'stimmi,' the name for the powdered mineral used as kohl to darken the eyes — a borrowing likely rooted in an Egyptian word for the same eye-paint. So the crystal that 'taught humanity to draw its own eyes on' is named, quite literally, for that ancient cosmetic; the '-ite' is the standard suffix mineralogists tack onto rock names.