mineral
Carnelian Agate
Chalcedony (SiO2 with iron oxide impurities)
Hardness: 6.5-7 (Mohs); Color: Red-orange to brownish-red; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64
- Hardness
- 6
- Color
- Red-orange to brownish-red
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Red-orange to brownish-red; Luster: Waxy to vitreous; 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, particularly volcanic lavas. The red tint is caused by iron oxide (hematite) impurities.
Uses & applications
Primarily used in jewelry (beads, cabochons), carvings, decorative seals, and as a collector's stone. Historically used for signet rings.
Geological facts
Carnelian was highly prized by Ancient Egyptians, who believed it had protective powers; it was also used by Roman and Greek civilizations for intaglio seals because wax does not stick to it.
Field identification & locations
Identified in the field by its translucent appearance, waxy luster, and distinctive orange-red hue. Commonly found in riverbeds or coastal areas where volcanic rock has eroded, notably in India, Brazil, and Uruguay.
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