Fluorite

Physical Properties

Hardness: 4 (Mohs scale); Color: green, purple, and clear; Luster: vitreous (glassy); Crystal structure: isometric/cubic; Cleavage: octahedral (perfect in four directions); Specific gravity: 3.175–3.184.

Formation & Geological History

Formed in hydrothermal veins, often associated with lead and silver ores. It also occurs in sedimentary rocks like limestone. It can be found in deposits dating from various geological eras, including the Paleozoic.

Uses & Applications

Used as a flux in steel making, in the manufacture of hydrofluoric acid, as a source of fluorine for water fluoridation, and as high-clarity lenses for telescopes and cameras. Also popular in jewelry and for mineral collecting.

Geological Facts

Fluorite is the origin of the term 'fluorescence' because many specimens glow under ultraviolet light. It is often called the 'most colorful mineral in the world.'

Field Identification & Locations

Identify in the field by its distinct cubic crystal habit, its 4-way cleavage, and its relative softness (it can be scratched by a steel knife but not a copper penny). Common locations include China, Mexico, South Africa, and the Illinois-Kentucky fluorspar district in the USA.

Identified on: 4/13/2026

Mode: Standard