mineral

Banded Agate (specifically Sardonyx or Red Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Red, orange, white, and brown; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific gravity: 2.58–2.64.

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

Identified March 31, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Red, orange, white, and brown; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific gravity: 2.58–2.64.

Formation & geological history

Formed through the deposition of silica from groundwater in the cavities of igneous rocks, such as volcanic lavas. The distinctive bands are created by cyclic changes in the impurities or mineral content of the silica-rich fluids over thousands of years.

Uses & applications

Commonly used in jewelry, lapidary arts, decorative carvings (like the heart shape shown), and precision pendulums or mortars and pestles in industrial settings due to its hardness.

Geological facts

Agate was one of the first materials used by ancient humans, with archaeological evidence of its use in beads and ornaments dating back to the Neolithic era. It is often named after the Achates River in Sicily where it was first discovered.

Field identification & locations

Identify by its characteristic parallel banding, translucency when held to light, and waxy texture when polished. It cannot be scratched by a steel knife. Common locations include Brazil, India, and the Lake Superior region of the US.

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