Rock Identifier
Banded Agate (specifically Carnelian Agate) (Silicon Dioxide (SiO2)) — mineral
mineral

Banded Agate (specifically Carnelian Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Translucent orange, reddish-brown, and white banding. Luster: Vitreous to waxy when polished. Crystal structure: Cryptocrystalline (hexagonal/trigonal). Cleavage: None, conchoidal fracture.

Hardness
6
Color
Translucent orange, reddish-brown, and white banding
Luster
Vitreous to waxy when polished
Identified More mineral
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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Translucent orange, reddish-brown, and white banding. Luster: Vitreous to waxy when polished. Crystal structure: Cryptocrystalline (hexagonal/trigonal). Cleavage: None, conchoidal fracture.

Formation & geological history

Formed in volcanic rock cavities (vesicles) from the deposition of silica from groundwater. The bands represent different stages of mineral deposition over thousands of years.

Uses & applications

Primary use is in jewelry as cabochons, beads, and wire-wrapped pendants. Also used for ornamental carvings, paperweights, and as a semi-precious collecting stone.

Geological facts

Agate was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore line of the river Achates in Sicily. Carnelian derives its color from iron oxide (hematite) impurities.

Field identification & locations

Identify in the field by its translucent quality, smooth waxy texture when broken, and characteristic concentric or parallel banding. Commonly found in Brazil, India, Uruguay, and Madagascar.