Rock Identifier
Banded Agate (specifically Carnelian Agate) (Cryptocrystalline Quartz (SiO2)) — mineral
mineral

Banded Agate (specifically Carnelian Agate)

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale). Color: Orange-red with white banding. Luster: Waxy to vitreous. Crystal structure: Trigonal/hexagonal. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Hardness
6
Color
Orange-red with white banding
Luster
Waxy to vitreous
Identified More mineral

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Physical properties

Hardness: 6.5-7 (Mohs scale). Color: Orange-red with white banding. Luster: Waxy to vitreous. Crystal structure: Trigonal/hexagonal. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Formation & geological history

Formed in cavities of volcanic rocks or ancient lavas. Silica-rich groundwater percolates through vesicles, depositing microcrystalline quartz in layers over thousands of years to create characteristic banding.

Uses & applications

Used extensively in jewelry (beads, cabochons), carvings, decorative ornaments, and as tumbled collector stones. Historically used for signet rings and amulets.

Geological facts

The red color is caused by iron oxide impurities. Agates were among the first materials used by humans for ornamental purposes, dating back to Ancient Greece and the Indus Valley Civilization.

Field identification & locations

Identify in the field by its distinct concentric banding, translucent edges, and waxy luster. Commonly found in riverbeds, lake shores (like Lake Superior), and volcanic regions in Brazil, India, and the USA.