mineral

Agate Geode

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored bands (white, tan, grey); Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Fracture: Conchoidal.

Hardness: 6
Color: Multi-colored bands (white, tan, grey)
Luster: Vitreous to waxy

Identified June 26, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored bands (white, tan, grey); Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Fracture: Conchoidal.

Formation & geological history

Formed within cavities (vesicles) of volcanic or sedimentary rocks. Silica-rich groundwater precipitates layers of microscopic quartz crystals over long periods, often associated with Cenozoic or Mesozoic volcanic activity.

Uses & applications

Used extensively in jewelry (cabochons), ornamental carvings, bookends, and collection specimens. Historically used for making precision mortars and pestles due to its hardness.

Geological facts

Agate was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore line of the Achates River in Sicily. Each agate specimen is unique due to the specific mineral impurities during formation.

Field identification & locations

Identify by its characteristic concentric banding, waxy texture, and extreme hardness (it will scratch glass). Often found in riverbeds or volcanic ash deposits in locations like Brazil, India, and the Western United States.