gemstone

Blue Topaz

Aluminum Silicate Fluoride Hydroxide, Al2SiO4(F,OH)2

AI-generated identification · may be incorrect

Hardness: 8.0 on Mohs scale. Color: Swiss Blue. Luster: Vitreous. Crystal system: Orthorhombic. Cleavage: Perfect basal. Specific gravity: 3.49-3.57.

Hardness: 8
Color: Swiss Blue
Luster: Vitreous

Identified July 9, 2026More gemstone →

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Physical properties

Hardness: 8.0 on Mohs scale. Color: Swiss Blue. Luster: Vitreous. Crystal system: Orthorhombic. Cleavage: Perfect basal. Specific gravity: 3.49-3.57.

Formation & geological history

Formed in igneous rocks like pegmatites and granites, as well as in alluvial deposits. While natural blue topaz exists, deep hues are typically achieved through irradiation and heat treatment of colorless topaz.

Uses & applications

Primarily used in high-quality jewelry (rings, pendants, earrings) and as a collector's gemstone. Industrial applications are limited due to high value.

Geological facts

Topaz is a pleochroic gem, meaning it can show different colors in different crystal directions. Blue topaz is the official state gemstone of Texas and the birthstone for December.

Field identification & locations

Identified by its high hardness (scratches glass/quartz) and distinct weight. In the field, look for well-defined prismatic crystals in pegmatitic veins. Commonly sourced from Brazil, Sri Lanka, and Nigeria.