Carnelian
Chalcedony var. Carnelian · Semi-Precious Gemstone / Decorative Stone
Crystal System
Trigonal crystal system with a microcrystalline/cryptocrystalline habit
Mineral Group
Silicates (Tectosilicate subgroup; Quartz group)
Chemical Formula
SiO2 (Silicon Dioxide) with impurities of iron oxide (hematite)
Formation Process
Forms through low-temperature silica-rich hydrothermal fluids filling cavities in volcanic rocks or through sedimentary precipitation.
About This Crystal
A translucent to semi-opaque chalcedony with a waxy to vitreous luster. This specimen shows a deep reddish-brown (sard-leaning) body color with characteristic uneven color distribution and small surface-reaching fractures.
Physical Characteristics
Color: Reddish-brown; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64; Fluorescence: Weakly inert to yellowish-white under longwave UV.
Optical Properties
Refractive Index: 1.530-1.540; Birefringence: Up to 0.004; Pleochroism: None; Optical Character: Aggregate (doubly refractive).
Hardness & Durability
Origin Region
Notable sources include India, Brazil, Madagascar, Uruguay, and Egypt; found in volcanic cavities and sedimentary environments.
Hardness & Durability
Mohs Hardness: 6.5 to 7; Toughness: Excellent (due to cryptocrystalline structure); Stability: Stable but can be affected by extreme heat.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners if the stone has surface-reaching fractures. Store away from harder gems like Topaz or Diamonds.
Rarity & Value
Common and widely available. Value is determined by color (vivid orange-red is preferred) and translucency. Often heat-treated to enhance red tones.
Special Characteristics
Exhibits a 'waxy' luster unique to chalcedony; may show subtle banding or cloud-like inclusions of iron oxide.
Lore & History
Used since ancient times in Mesopotamia and Egypt for cylinder seals and amulets. Symbolizes courage and vitality; traditionally linked to the sacral chakra in modern lore.