mineral

Agate (within host rock)

Agate (Quartz variety SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Blue-gray, white, and translucent brown bands; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None, exhibits conchoidal fracture.

Hardness: 6
Color: Blue-gray, white, and translucent brown bands
Luster: Vitreous to waxy

Identified July 12, 2026More mineral →

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Physical properties

Formation & geological history

Formed from silica-rich groundwater depositing layers within cavities of volcanic or metamorphic rocks. The banding patterns represent different stages of mineral deposition over thousands of years.

Uses & applications

Used in jewelry (cabochons), ornamental carvings, burnishing tools, mortar and pestles for laboratories, and as a popular collector's specimen.

Geological facts

Agate is a variety of chalcedony. The concentric rings seen in this specimen are classic 'fortification' patterns, so named because they resemble the floor plans of old European forts.

Field identification & locations

Can be identified by the distinctive waxy luster and concentric banding once broken or cut. Often found in riverbeds or areas with ancient volcanic activity like Brazil, Uruguay, or the Lake Superior region.

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