sedimentary/mineral
Ferruginous Quartz (Carnelian/Sardine Jasper)
Silicon Dioxide (SiO2) with Iron Oxide (Fe2O3) impurities
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, orange, burnt sienna; Luster: Vitreous to waxy; Structure: Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Reddish-brown, orange, burnt sienna
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, orange, burnt sienna; Luster: Vitreous to waxy; Structure: Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed in silica-rich sedimentary or volcanic cavities where groundwater enriched with iron oxides permeates the silica gel, depositing layers that eventually harden into microcrystalline quartz through dehydration and pressure.
Uses & applications
Primarily used in jewelry as cabochons, lapidary carvings, metaphysical stones, and architectural accents for ornamental stone applications.
Geological facts
The reddish color is caused by the presence of hematite or goethite. In ancient times, carnelian was believed to bestow courage and was frequently used in Roman signet rings to prevent wax from sticking to the seal.
Field identification & locations
Identify by its high hardness (it will scratch glass), waxy luster, and conchoidal fracture. Often found in riverbeds or coastal rocky areas. Look for translucent edges when held to the light.
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