gemstone

Blue Topaz

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

Hardness: 8.0 on Mohs scale; Color: Cyan to Swiss Blue; Luster: Vitreous (glassy); Crystal structure: Orthorhombic; Specific Gravity: 3.49-3.57; Cleavage: Perfect basal.

Hardness: 8
Color: Cyan to Swiss Blue
Luster: Vitreous (glassy)

Identified July 8, 2026More gemstone →

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Physical properties

Hardness: 8.0 on Mohs scale; Color: Cyan to Swiss Blue; Luster: Vitreous (glassy); Crystal structure: Orthorhombic; Specific Gravity: 3.49-3.57; Cleavage: Perfect basal.

Formation & geological history

Formed in igneous environments such as granitic pegmatites and rhyolite, often appearing in the late stages of magma cooling where fluorine vapors are present. Most deep blue specimens are natural colorless topaz that has been irradiated and heat-treated.

Uses & applications

Primarily used in the jewelry industry for rings, earrings, and pendants; also a popular specimen for gemstone collectors.

Geological facts

Topaz is the birthstone for November, and blue topaz specifically is synonymous with the month of December. Natural vivid blue topaz is incredibly rare in nature; most commercial stones are colored through artificial treatment.

Field identification & locations

Identify by its high hardness (scratches quartz), high density, and smooth, perfect basal cleavage. It is commonly found in Brazil, Nigeria, Sri Lanka, and the United States (Texas and Colorado).

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