Blue Chalcedony

Physical Properties

Hardness: 6.5–7 (Mohs); Color: Waxy translucent blue; Luster: Vitreous to waxy; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; SG: 2.58–2.64.

Formation & Geological History

Formed in low-temperature hydrothermal environments where silica-rich fluids deposit in cavities of volcanic and sedimentary rocks. Common in basaltic geodes.

Uses & Applications

Used primarily in jewelry as cabochons, lapidary carvings, beadwork, and by mineral collectors for its aesthetic translucency.

Geological Facts

Its name is derived from the ancient Greek town Chalcedon. Unlike crystalline quartz (like amethyst), chalcedony is made of microscopic interlocking fibers of quartz and moganite.

Field Identification & Locations

Identify by its waxy luster, conchoidal fracture, and lack of visible crystal faces. Found commonly in Brazil, Namibia, Turkey, and the USA (Oregon/California).

Identified on: 4/24/2026

Mode: Standard