gemstone

Blue topaz cross pendant

Topaz, Al₂SiO₄(F,OH)₂; likely faceted blue topaz

AI-generated identification · may be incorrect

Blue, transparent, vitreous luster, orthorhombic crystal structure; Mohs hardness 8, with perfect basal cleavage. The pictured stones are cut and set in metal, so weight and exact properties cannot be assessed visually.

Identified October 3, 2026More gemstone →

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Physical properties

Formation & geological history

Topaz crystallizes in silica-rich igneous rocks, especially pegmatites and rhyolites, and can also occur in alluvial deposits. Natural topaz formed across many geological ages; much commercial blue topaz is color-treated to produce its hue.

Uses & applications

Used in jewelry and collecting; topaz is also valued as a durable gemstone, though its cleavage makes it vulnerable to sharp impacts.

Geological facts

Most blue topaz on the market is irradiated and heat-treated colorless or pale topaz; treatment is accepted in the trade and should be disclosed.

Field identification & locations

A gemologist can verify topaz using refractive and density tests; blue glass and other blue gems can look similar. Topaz occurs in Brazil, Pakistan, Russia, Nigeria, and the United States.