mineral

Agate Sliced Nodule

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Translucent white, grey, and brown banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Translucent white, grey, and brown banding
Luster: Waxy to vitreous

Identified July 10, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Translucent white, grey, and brown banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64.

Formation & geological history

Formed as secondary deposits in hollow cavities of volcanic rocks (geodes) where silica-rich groundwater precipitated layers of chalcedony over thousands of years.

Uses & applications

Primarily used for ornamental decoration, jewelry, lapidary arts, and as paperweights or coasters. Historically used for burnishing tools.

Geological facts

Agates are named after the Achates River in Sicily where they were first discovered. This specimen is a slice of a larger nodule, showing typical concentric banding and a translucent center.

Field identification & locations

Identify by its waxy luster, variety of colors, and characteristic curved bands. It is commonly found in volcanic regions of Brazil, Uruguay, and the United States (Lake Superior region).