gemstone

Blue Chalcedony (Moonstone-like / Agate)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Translucent sky-blue to lavender-blue with soft adularescence or optical sheen. Luster: Vitreous to waxy. Crystal System: Microcrystalline trigonal.

Hardness: 6
Luster: Vitreous to waxy

Identified July 27, 2026More gemstone →

Explore Blue Chalcedony (Moonstone-like / Agate) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Translucent sky-blue to lavender-blue with soft adularescence or optical sheen. Luster: Vitreous to waxy. Crystal System: Microcrystalline trigonal.

Formation & geological history

Formed through low-temperature precipitation of silica-rich hydrothermal fluids in cavities, volcanic rock pockets, or sedimentary environments.

Uses & applications

Popular gemstone used in jewelry making (rings, pendants, beads) and ornamental carvings due to its pleasing soft blue color and translucency.

Geological facts

Blue chalcedony exhibits a soft internal glow caused by the Tyndall effect—light scattering off fine fibrous inclusions within the quartz matrix. It is sometimes trade-named 'Holly Blue' or 'Blue Lace' depending on banding.

Field identification & locations

Identified by its cryptocrystalline quartz hardness (scratches glass, resists steel), smooth cabochon finish, and distinct translucent pale blue hue. Found globally in Namibia, Turkey, Madagascar, and Brazil.