purple octagon fluorite
These large crystals have formed themselves into an octagon shape.
Fluorite is used as a flux in smelting iron, aluminum, and other metal alloys and in welding. It is also used in the manufacture of glass, enamel glazes, ceramics, cement, and other chemical compounds. Fluoride, derived from fluorite, is used in toothpaste, optical lenses, concrete hardeners, organic chemicals, plastics, refrigerants, nonstick coatings, lubricants, stain repellants, dyes, herbicides, anesthetics, cleaning solvents, and degreasing and foaming agents.