gemstone

Blue topaz pendant

Topaz (Al₂SiO₄(F,OH)₂), likely treated blue topaz

AI-generated identification · may be incorrect

Mohs hardness 8; typically colorless to pale blue with vitreous luster, orthorhombic crystals, and perfect basal cleavage. The faceted blue stone is set in a gold-colored metal pendant, likely jewelry-grade topaz rather than a raw specimen.

Identified August 25, 2026More gemstone →

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Physical properties

Formation & geological history

Topaz forms in cavities and late-stage veins of silica-rich igneous rocks, especially granites and rhyolites, from hydrothermal fluids; deposits commonly range from Paleozoic to younger. Blue color in commercial stones is usually produced by irradiation followed by controlled heating.

Uses & applications

Used primarily in jewelry; large blue topaz is affordable and widely sold. Industrial topaz has limited use because cleavage makes it difficult to process.

Geological facts

Natural blue topaz is uncommon; most vivid blue examples are treated colorless topaz. Common commercial grades include Swiss blue, sky blue, and London blue.

Field identification & locations

Identify topaz by its high hardness, strong vitreous luster, and cleavage; confirm with gemological testing because blue zircon, aquamarine, and synthetic materials can look similar. Important localities include Brazil, Pakistan, Nigeria, Sri Lanka, and the United States.