Carnelian
Quartz var. Carnelian · Semi-Precious Gemstone
Crystal System
Trigonal - Microcrystalline; typically occurs as massive, botryoidal, or as water-worn pebbles.
Mineral Group
Silicates (Tectosilicate subgroup; Chalcedony variety)
Chemical Formula
SiO2 (Silicon Dioxide) with iron oxide (Fe2O3) impurities
Formation Process
Found in hydrothermal environments and volcanic cavities (vugs) where silica-rich fluids deposit at relatively low temperatures.
About This Crystal
Translucent to semi-opaque chalcedony with a waxy to vitreous luster. Features a warm reddish-orange to brownish-red color, often with subtle banding or cloud-like inclusions.
Physical Characteristics
Color: Orange, red, brownish-red. Streak: White. Cleavage: None. Fracture: Conchoidal. Specific Gravity: 2.58–2.64. Fluorescence: Usually inert or weak yellowish.
Optical Properties
Refractive Index: 1.530–1.540. Birefringence: Up to 0.004. Pleochroism: None. Optical Effect: Translucency allows for a deep, glowing quality when backlit.
Hardness & Durability
Origin Region
Notable sources include India (Gujarat), Brazil, Uruguay, Madagascar, and Botswana; often found in volcanic environments.
Hardness & Durability
Mohs Hardness: 6.5–7. Excellent durability and toughness for jewelry as it lacks cleavage points.
Care & Maintenance
Safe to clean with warm soapy water and a soft brush. While stable, avoid extreme heat which can alter color, and keep away from harsher industrial chemicals.
Rarity & Value
Common and affordable. Value is determined by color intensity (redder is often preferred) and clarity. Heat treatment of pale chalcedony to create carnelian is very common.
Special Characteristics
Often shows internal translucency and 'swirly' growth patterns; color intensity is derived from the oxidation of iron impurities.
Lore & History
Used since the Neolithic period; highly prized in Ancient Egypt for amulets (the 'Blood of Isis') and in Roman times for signet rings and seals because hot wax does not stick to it.