mineral

Agate (Polished Nodule)

Agate (Silicon Dioxide, SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored bands (brown, white, blue-grey); Luster: Vitreous to waxy; Crystal structure: Trigonal (Cryptocrystalline); Cleavage: None; Specific gravity: 2.58–2.64.

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

Identified April 6, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in volcanic or metamorphic rock cavities. Silica-rich groundwaters deposit microcrystalline quartz over thousands of years. Often found in ancient lava flows.

Uses & applications

Used extensively in jewelry (cabochons), interior decoration, precision pendulums, and as mortar and pestles in labs due to its hardness and chemical resistance.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. Many specimens are dyed to enhance their colors, though natural banding is highly prized by collectors.

Field identification & locations

Identify in the field by its waxy luster on fractured surfaces and concentric banding. Commonly found in Brazil, Uruguay, and Lake Superior regions. Collectors look for unique inclusions or rare colors.

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