Blue Chalcedony

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Pale blue to lavender; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Formation & Geological History

Formed from silica-rich hydrothermal fluids depositing in volcanic rock cavities or sedimentary environments at relatively low temperatures. Often found in geodes or as botryoidal masses.

Uses & Applications

Used primarily in lapidary arts, jewelry (cabochons, beads), and as a collector's gemstone. Also used historically for seals and cameos.

Geological Facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification. The blue color is often the result of the Tyndall effect, where light is scattered by minute inclusions.

Field Identification & Locations

Identify by its waxy luster, conchoidal fracture, and lack of visible crystalline structure compared to quartz. Common in Namibia, Turkey, Malawi, and the USA (California and Oregon).

Identified on: 4/14/2026

Mode: Standard