mineral
Carnelian Agate
Silicon dioxide (SiO2) with iron impurities
Hardness: 6.5-7 (Mohs); Color: Orange, reddish-brown, and white/translucent; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Specific gravity: 2.58-2.64
- Hardness
- 6
- Color
- Orange, reddish-brown, and white/translucent
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Orange, reddish-brown, and white/translucent; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Specific gravity: 2.58-2.64
Formation & geological history
Formed as a cryptocrystalline variety of quartz within cavities of volcanic rocks (basalt/rhyolite) or sedimentary environments through the precipitation of silica from groundwater containing iron oxide.
Uses & applications
Used primarily in lapidary work for jewelry, cabochons, carved figurines (like this heart), and pocket stones for collectors.
Geological facts
Carnelian was used widely in the ancient world for signet rings and seals because hot wax does not stick to it. It has been used as a gemstone for over 4,500 years, dating back to ancient Ur and Egypt.
Field identification & locations
Identify by its waxy luster, translucency, and the lack of visible grain. Commonly found in Brazil, India, Uruguay, and Madagascar. This specimen has been carved and polished into a heart shape.
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