mineral

Chalcedony Geode

Silicon Dioxide (SiO2)

Hardness of 6.5 to 7 on the Mohs scale, grayish-blue color, vitreous to waxy luster, microcrystalline crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65.

Identified July 28, 2026More mineral →

Explore 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 of 6.5 to 7 on the Mohs scale, grayish-blue color, vitreous to waxy luster, microcrystalline crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65.

Formation & geological history

Formed when mineral-rich groundwater or hydrothermal fluids deposit silica in hollow cavities of sedimentary or volcanic rocks over millions of years.

Uses & applications

Used in ornamental carvings, gemstone jewelry, lapidary art, and cherished by mineral collectors.

Geological facts

Geodes start as bubbles in volcanic rock or animal burrows in sedimentary rock, slowly filling inward with microscopic quartz crystals to form a hollow center lined with crystals.

Field identification & locations

Easily identified by its nodular exterior and hollow center lined with microcrystalline quartz or chalcedony. Commonly found globally in volcanic regions such as Brazil, Mexico, and the western United States.