mineral

Blue Chalcedony Geode

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Pale blue to milky grey; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (Cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Pale blue to milky grey
Luster: Waxy to vitreous

Identified July 21, 2026More mineral →

Explore Blue Chalcedony Geode 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 Mohs; Color: Pale blue to milky grey; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (Cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Formation & geological history

Formed through the deposition of silica-rich fluids in volcanic cavities or sedimentary pockets. Over millions of years, microcrystalline quartz layers build up from the walls inward. Found in basaltic or rhyolitic host rocks.

Uses & applications

Used primarily in lapidary arts, jewelry, decorative ornaments, and as meditation stones in alternative healing practices.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen with a standard microscope. Blue varieties are particularly prized for their ethereal glow caused by the Tyndall effect.

Field identification & locations

Identify by its waxy luster on the face and the rough, cauliflower-like texture of its outer 'rind'. Check for translucency under a bright light source. Common locations include Brazil, Malawi, and Namibia.