gemstone

Blue Chalcedony

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs); Color: Pale blue to sky blue; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None; SG: 2.6

Hardness: 6
Color: Pale blue to sky blue
Luster: Vitreous to waxy

Identified July 7, 2026More gemstone →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Pale blue to sky blue; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None; SG: 2.6

Formation & geological history

Formed through the deposition of silica from aqueous solutions, often in cavities of volcanic rocks or sedimentary environments. It is a microcrystalline variety of quartz.

Uses & applications

Used primarily in jewelry as beads and cabochons, and in ornamental carvings or collector specimens.

Geological facts

Chalcedony was used by ancient civilizations for cylinder seals and amulets. The specific blue hue is often caused by the Tyndall effect, where light scatters off tiny particles within the stone.

Field identification & locations

Identify by its waxy luster, lack of visible crystals, and hardness. Found in locations like Namibia, Turkey, India, and the United States (western states). Look for a milky translucency.