mineral

Agate

Silicon dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: White, bluish-gray, and tan; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Trigonal); Cleavage: None; Specific gravity: 2.58-2.64

Hardness: 6
Color: White, bluish-gray, and tan
Luster: Waxy to vitreous

Identified May 20, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: White, bluish-gray, and tan; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Trigonal); Cleavage: None; Specific gravity: 2.58-2.64

Formation & geological history

Formed in cavities of volcanic rock or ancient hydrothermal veins where silica-rich groundwater deposits layers of microcrystalline quartz over thousands of years.

Uses & applications

Commonly used for lapidary arts, jewelry (cabochons), burnishing tools, and as a collector's specimen due to its unique banding patterns.

Geological facts

Agate is a variety of chalcedony. The name comes from the Achates River in Sicily where they were first discovered by the Greek philosopher Theophrastus.

Field identification & locations

Identify in the field by its translucent edges, waxy texture, and concentric banding. Commonly found in riverbeds or volcanic regions like Brazil, Oregon, and the Lake Superior region.