Rock Identifier
Carnelian Agate (Silicon Dioxide (SiO2) with Iron Impurities) — mineral
mineral

Carnelian Agate

Silicon Dioxide (SiO2) with Iron Impurities

Hardness: 6.5-7 (Mohs scale); Color: Translucent orange to reddish-brown with banding; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.64.

Hardness
6
Color
Translucent orange to reddish-brown with banding
Luster
Vitreous to waxy
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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Translucent orange to reddish-brown with banding; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.64.

Formation & geological history

Formed in volcanic or sedimentary rocks through the deposition of silica-rich groundwater within gas cavities (vesicles). The reddish-orange color is caused by iron oxide impurities. These can range from millions to hundreds of millions of years in age.

Uses & applications

Commonly used in lapidary work, jewelry (cabochons, beads), decorative carvings, and as a popular specimen for crystal collectors. Historically used for signet rings and seals because wax doesn't stick to it.

Geological facts

Ancient Egyptians referred to Carnelian as the 'setting sun.' It was one of the first stones used for jewelry-making in human history, dating back to the Neolithic period. The banding seen in this specimen identifies it specifically as an Agate variety of Chalcedony.

Field identification & locations

Identify in the field by its translucency (when held to light), waxy luster, and distinctive concentric or curved banding. Common in riverbeds and areas with ancient volcanic activity like the Pacific Northwest (USA), Brazil, and India.

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