Carnelian
Quartz var. Carnelian · Semi-Precious Gemstone
Crystal System
Trigonal; Cryptocrystalline (Microcrystalline aggregate) typically appearing massive or as nodules
Mineral Group
Silicates (Tectosilicates)
Chemical Formula
SiO2 with trace Fe2O3 (Iron Oxide)
Formation Process
Secondary process where silica-rich fluids deposit in cavities (vesicles) of volcanic rocks at low temperatures, or through the weathering of silicate rocks.
About This Crystal
A translucent to semi-opaque chalcedony with a waxy to vitreous luster. This specimen shows a deep reddish-brown (sard-leaning) saturation with a smooth, polished surface and a visible fracture/inclusion area showing some lighter internal banding.
Physical Characteristics
Color: Red-orange to brownish-red; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64; Fluorescence: Weak to inert.
Optical Properties
Refractive Index: 1.530-1.540; Birefringence: Up to 0.004; Pleochroism: None; Optical character: Aggregate; Phenomena: Rare banding (agate-carnelian).
Hardness & Durability
Origin Region
India (famous for high quality), Brazil, Uruguay, Madagascar, and Egypt. Found in volcanic cavities and sedimentary gravels.
Hardness & Durability
Mohs Hardness: 6.5-7; Toughness: Very Good (due to microcrystalline structure); Stable to light but can be sensitive to extreme heat.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners if there are visible fractures. Generally stable but store separately to avoid scratching softer stones.
Rarity & Value
Common; Value is determined by color intensity (redder is better) and translucency. Frequent treatments include heating lighter chalcedony or dyeing to enhance red tones.
Special Characteristics
Translucency when held to light; may show faint banding typical of agate; iron oxide impurities provide the distinct red-brown coloration.
Lore & History
Highly significant in Ancient Egypt (Set's stone) and Rome for signet rings and seals because hot wax does not stick to it. Historically associated with courage, vitality, and the sacral chakra in traditional lore.