Blue Chalcedony

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Pale blue, lavender-blue; Luster: Vitreous to waxy; Structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; SG: 2.6

Formation & Geological History

Formed in volcanic cavities or sedimentary environments via silica-rich water precipitation. It occurs as a secondary mineral in igneous rocks or as a replacement mineral in petrified wood.

Uses & Applications

Predominantly used as a gemstone for jewelry (cabochons, beads), decorative carvings, and as a collector's specimen.

Geological Facts

In antiquity, it was often used for seals and amulets. Significant historical deposits were found in the ancient Greek town of Chalcedon. Some specimens show a slight 'adularescence' similar to moonstone.

Field Identification & Locations

Identify by its waxy luster, translucency, and lack of visible crystal grains. Common locations include Namibia, Turkey, India, and the USA (California/Oregon). It is harder than glass but won't show the cleavage plane found in blue lace agate.

Identified on: 4/14/2026

Mode: Standard