mineral

Blue Chalcedony

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Pale blue to lavender-grey; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6

Hardness: 6
Color: Pale blue to lavender-grey
Luster: Waxy to vitreous

Identified May 18, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Pale blue to lavender-grey; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6

Formation & geological history

Formed through low-temperature deposition of silica-rich fluids in cavities of volcanic and sedimentary rocks. Common in basaltic geodes. Ages range widely from Tertiary to Precambrian.

Uses & applications

Extensively used in lapidary arts for carvings, cabochons, and beads. Highly valued by collectors as polished points (like shown) and in ornamental decor.

Geological facts

Unlike crystalline quartz, chalcedony is composed of microscopic fibers. The blue color is due to the Tyndall effect—the scattering of light by fine particles rather than chemical impurities.

Field identification & locations

Identify by its characteristic waxy luster and translucency. It lacks the visible crystalline structure of quartz amethyst. Commonly sourced from Turkey, Namibia, and Brazil.