sedimentary

Banded Agate

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Red, orange, white, and brown bands; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.60-2.65

Hardness: 6
Color: Red, orange, white, and brown bands
Luster: Vitreous to waxy

Identified July 8, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Red, orange, white, and brown bands; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.60-2.65

Formation & geological history

Formed primary by the deposition of silica from groundwater in the cavities of igneous rocks such as basalt or within sedimentary rocks. The banding represents rhythmic crystallization over thousands of years. Often associated with volcanic activity from the Proterozoic or Mesozoic eras.

Uses & applications

Extensively used in jewelry (cabochons), ornamental carvings, decorative items, and historically for precision mechanical parts like mortar and pestles due to its hardness.

Geological facts

Agate is the state gemstone of several US states including Minnesota and Kentucky. The name originates from the Achates River in Sicily where it was first discovered in ancient times.

Field identification & locations

Identified by its distinctive parallel, curved, or concentric banding and waxy texture. In the field, look for nodules with a rough, pitted exterior and translucent interior when chipped. Common in Brazil, India, and the Lake Superior region of the USA.