Rock Identifier
Fluorite (left), Sodalite (middle), Dumortierite/Tumbled Quartzite (right) (Calcium Fluoride (CaF2), Sodium Aluminum Silicate Chloride (Na8(Al6Si6O24)Cl2), Aluminum Borosilicate (Al7(BO3)(SiO4)3O3)) — mineral
mineral

Fluorite (left), Sodalite (middle), Dumortierite/Tumbled Quartzite (right)

Calcium Fluoride (CaF2), Sodium Aluminum Silicate Chloride (Na8(Al6Si6O24)Cl2), Aluminum Borosilicate (Al7(BO3)(SiO4)3O3)

Hardness: 4-7 Mohs. Fluorite (left): Transparent/translucent with green/purple banding, glassy luster. Sodalite (middle): Deep royal blue with white calcite veining, greasy/vitreous luster. Dumortierite (right): Dull grey-blue, matte to vitreous luster, dense.

Hardness
4-7 Mohs
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Physical properties

Hardness: 4-7 Mohs. Fluorite (left): Transparent/translucent with green/purple banding, glassy luster. Sodalite (middle): Deep royal blue with white calcite veining, greasy/vitreous luster. Dumortierite (right): Dull grey-blue, matte to vitreous luster, dense.

Formation & geological history

Fluorite: Formed in hydrothermal veins through hot mineral solutions. Sodalite: Found in alkaline igneous rocks like nepheline syenites. Dumortierite: Metamorphic mineral formed in aluminum-rich pegmatites.

Uses & applications

Used primarily as decorative gemstones, healing stones (metaphysical collectors), and in industrial applications (fluorite is used as a flux in smelting and in high-performance optics).

Geological facts

Fluorite is the origin of the term 'fluorescence' as it glows under UV light. Sodalite is often mistaken for Lapis Lazuli but lacks the gold pyrite inclusions and is significantly less expensive.

Field identification & locations

Identify Fluorite by its soft hardness (scratched by glass) and cube cleavage. Identify Sodalite by its distinctive white marbling on blue. Identify Dumortierite by its fibrous habit and hardness (scratches glass). Locations: South Africa, Brazil, China, and USA (Arizona/Illinois).

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