Fluorite

General

Category: Halide mineral

Formula: CaF2

IMA symbol: Flr

Strunz classification: 3.AB.25

Crystal system: Isometric

Crystal class: Hexoctahedral (m3m) H–M symbol: (4/m 3 2/m)
(cF12)

Space group: Fm3m (No. 225)

Unit cell: a = 5.4626 Å; Z = 4


Identification

Color: Colorless, although samples are often deeply colored owing to impurities; Purple, lilac, golden-yellow, green, blue, pink, champagne, brown.

Crystal habit: Well-formed coarse sized crystals; also nodular, botryoidal, rarely columnar or fibrous; granular, massive

Twinning: Common on {111}, interpenetrant, flattened

Cleavage: Octahedral, perfect on {111}, parting on {011}

Fracture: Subconchoidal to uneven

Tenacity: Brittle

Mohs scale hardness: 4 (defining mineral)

Luster: Vitreous

Streak: White

Diaphaneity: Transparent to translucent

Specific gravity: 3.175–3.184; to 3.56 if high in rare-earth elements

Optical properties: Isotropic; weak anomalous anisotropism; moderate relief

Refractive index: 1.433–1.448

Fusibility: 3

Solubility: slightly water soluble and in hot hydrochloric acid

Other characteristics: May be fluorescent, phosphorescent, thermoluminescent, and/or triboluminescent

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