mineral

Blue Topaz

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

AI-generated identification · may be incorrect

Hardness: 8.0, Color: Light to vibrant blue (London, Swiss, or Sky), Luster: Vitreous (glassy), Crystal Structure: Orthorhombic, Cleavage: Perfect basal (one direction), Specific Gravity: 3.49–3.57

Hardness: 8

Identified May 24, 2026More mineral →

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Physical properties

Hardness: 8.0, Color: Light to vibrant blue (London, Swiss, or Sky), Luster: Vitreous (glassy), Crystal Structure: Orthorhombic, Cleavage: Perfect basal (one direction), Specific Gravity: 3.49–3.57

Formation & geological history

Formed in acidic igneous rocks like granite and rhyolite, often in pegmatite veins or cavity fillings. Natural blue topaz is rare; most commercial specimens are colorless topaz treated with irradiation and heat.

Uses & applications

Primarily used as a gemstone in high-end and fashion jewelry (rings, pendants, earrings). Industrial use is limited due to heat sensitivity, though natural colorless topaz is sometimes a source of fluorine.

Geological facts

Topaz is the birthstone for November, though blue topaz is often used as an alternative for December. It is the state gemstone of Texas. Most blue topaz in the market is irradiated to achieve its deep color.

Field identification & locations

Identify by its hardness (scratches glass/quartz) and high refractive index. In the field, it is found in alluvial deposits or within granite pegmatites. Common locations include Brazil, Sri Lanka, and Russia.