Rock Identifier
Banded Agate (Agate (Silicon Dioxide, SiO2)) — mineral
mineral

Banded Agate

Agate (Silicon Dioxide, SiO2)

Hardness: 6.5-7 Mohs; Color: White, grey, and brown bands; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.58-2.64

Hardness
6
Color
White, grey, and brown bands
Luster
Waxy to vitreous
Identified More mineral

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Physical properties

Hardness: 6.5-7 Mohs; Color: White, grey, and brown bands; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.58-2.64

Formation & geological history

Formed in cavities of volcanic rocks or ancient lavas, where silica-rich groundwater deposited layers of microcrystalline quartz over thousands of years. It can also form in sedimentary environments.

Uses & applications

Commonly used in jewelry, decorative carvings, metaphysical collections, and historically for precision bearings due to its hardness.

Geological facts

Agate is a variety of chalcedony. The banding is caused by rhythmic crystallization during the deposition process. It is often named after its locality, such as Botswana or Lake Superior agate.

Field identification & locations

Identify in the field by its distinct colorful banding, waxy texture, and conchoidal fracture. Often found as nodules in stream beds or weathered out of basaltic outcrops.