mineral

Chalcedony (Botryoidal Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs). Color: Grayish-blue to translucent white. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Specific gravity: 2.6-2.64. No cleavage, conchoidal fracture.

Hardness: 6
Color: Grayish-blue to translucent white
Luster: Waxy to vitreous

Identified May 5, 2026More mineral →

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: Grayish-blue to translucent white. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Specific gravity: 2.6-2.64. No cleavage, conchoidal fracture.

Formation & geological history

Formed from the deposition of silica from hydrothermal solutions in the cavities of volcanic rocks (vugs) or and sedimentary environments. Often found in basaltic lava voids.

Uses & applications

Used primarily for ornamental purposes, jewelry (cabochons), lapidary art, and as a semi-precious gemstone collector specimen.

Geological facts

The term chalcedony comes from the ancient Greek town of Chalcedon in Asia Minor. It is a fibrous form of silica that can take on many forms, including carnelian and onyx.

Field identification & locations

Identify by its waxy luster, hardness (it will scratch glass), and the characteristic botryoidal (grape-like) or bubbly texture in its cavities. Common in volcanic regions.