Carnelian
Quartz var. Carnelian · Semi-Precious Gemstone
Crystal System
Trigonal/Hexagonal; typically microcrystalline (cryptocrystalline) with a massive or nodular habit.
Mineral Group
Silicates (Tectosilicate subgroup; Chalcedony variety)
Chemical Formula
SiO2 (Silicon Dioxide) with iron oxide (Fe2O3) impurities
Formation Process
Formed at low temperatures in volcanic rocks (filling cavities/vesicles) or through the weathering of sedimentary rocks via silica-rich fluids.
About This Crystal
A translucent to semi-opaque variety of chalcedony. This specimen exhibits a deep reddish-orange color with a waxy to vitreous luster. It shows a smooth, rounded (cabochon or tumbled) shape with a visible conchoidal fracture where chipped.
Physical Characteristics
Color: Red-orange to brownish-red; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58–2.64; Fluorescence: Usually inert but may show weak yellow-white.
Optical Properties
Refractive Index: 1.530–1.540; Birefringence: Weak (up to 0.004); Pleochroism: None; Optical Character: Uniaxial positive (aggregate).
Hardness & Durability
Origin Region
India (notable for high quality), Brazil, Uruguay, Madagascar, and Egypt; typically found in volcanic cavities and sedimentary environments.
Hardness & Durability
Mohs Hardness: 6.5–7; Toughness: Excellent (due to cryptocrystalline structure); Stability: Stable, though extreme heat can darken or alter color.
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid harsh chemicals and ultrasonic cleaners if the stone has surface-reaching fractures. Store separately from harder gems like diamond or sapphire.
Rarity & Value
Common; Value is driven by color saturation (deep red is preferred) and translucency. Heat treatment is very common to enhance the reddish tones of paler agates.
Special Characteristics
Shows characteristic waxy luster and translucency when held to light. Some specimens may show faint banding (transitioning into Sardonyx).
Lore & History
Historically used in Ancient Egypt for amulets and signet rings (the 'Seal of Mohammed'). Traditionally associated with the Sacral Chakra, vitality, motivation, and physical energy.