Fluorite

Physical Properties

Hardness: 4 on Mohs scale. Color: Clear, green, and purple (zoning visible). Luster: Vitreous (glassy). Crystal Structure: Isometric/Cubic. Cleavage: Perfect octahedral. Specific Gravity: 3.175–3.184.

Formation & Geological History

Formed through hydrothermal activity, often in veins within limestone or as an accessory mineral in igneous rocks like granite. Found in many geological ages ranging from Paleozoic to Cenozoic.

Uses & Applications

Used as a flux in steelmaking (smelting), production of hydrofluoric acid, high-clarity optical lenses, and as a popular collector's mineral and gemstone for jewelry (though soft).

Geological Facts

Fluorite exhibits 'fluorescence' under UV light, a term actually named after the mineral itself. It is the state mineral of Illinois and is known as 'the most colorful mineral in the world'.

Field Identification & Locations

Identify in the field by its distinct cubic crystal habit, perfect cleavage (forming small triangles/pyramids when broken), and 4.0 hardness which can be scratched by a steel nail but not a copper penny. Found in areas like Illinois-Kentucky district (USA), China, and England.

Identified on: 5/1/2026

Mode: Standard