mineral

Agate Geode

Chalcedony (cryptocrystalline SiO2)

Hardness: 6.5-7 Mohs; Color: Grey, white, and translucent; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Hardness: 6
Color: Grey, white, and translucent
Luster: Waxy to vitreous

Identified March 12, 2026More mineral →

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Physical properties

Formation & geological history

Formed via the deposition of silica from groundwater within cavities (vugs) of igneous or sedimentary rocks. This specimen shows concentric layering of chalcedony around a hollow or filled center, typical of volcanic gas bubble origins.

Uses & applications

Commonly used for lapidary work, jewelry (cabochons), interior decoration, and as a popular specimen for mineral collectors.

Geological facts

Agates are often found as nodules inside volcanic rocks; when they are hollow and lined with crystals, they are called geodes. They have been used as amulets and decorative objects since the Neolithic era.

Field identification & locations

Identified by its waxy luster, hardness (will scratch glass), and characteristic banding or cloud-like patterns. Common in volcanic regions such as Brazil, Uruguay, and the western United States.