mineral

Blue Topaz (facetted in jewelry)

Aluminum silicate fluoride hydroxide (Al2SiO4(F,OH)2)

Hardness: 8 on Mohs scale; Color: typically pale blue-to-medium blue; Luster: Vitreous; Crystal structure: Orthorhombic; Cleavage: Perfect basal.

Hardness: 8 on Mohs scale
Color: typically pale blue-to-medium blue
Luster: Vitreous

Identified March 13, 2026More mineral →

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Physical properties

Hardness: 8 on Mohs scale; Color: typically pale blue-to-medium blue; Luster: Vitreous; Crystal structure: Orthorhombic; Cleavage: Perfect basal.

Formation & geological history

Formed in igneous rocks, specifically in pegmatites and rhyolites, and often found as water-worn pebbles in stream beds. Most blue topaz on the market is irradiated and heat-treated to produce uniform blue shades.

Uses & applications

Predominantly used as a gemstone in jewelry (rings, earrings, necklaces) due to its excellent hardness and relatively low cost compared to sapphire or blue diamond.

Geological facts

Natural blue topaz is actually quite rare in nature; most affordable commercial blue topaz starts as colorless or pale material and undergoes laboratory treatment. It is the birthstone for December and the state gemstone of Texas.

Field identification & locations

Identify by its high brilliance, lack of visible inclusions in high-quality specimens, and its significant hardness (it will scratch glass and quartz). In the field, it is often found in alluvial deposits or within cavity linings of igneous rocks like granite.

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