Carnelian Agate within Matrix
Quartz var. Agate (subvariety Carnelian) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal symmetry; Microcrystalline (Cryptocrystalline) aggregate; typically occurs in massive, nodular, or geode-filling habits.
Mineral Group
Silicates (Tectosilicates); Chalcedony group
Chemical Formula
SiO2 (Silicon Dioxide) with Fe2O3 (Iron Oxide) inclusions
Formation Process
Hydrothermal / Sedimentary; formed by the deposition of silica-rich fluids in volcanic vesicles or rock cavities at relatively low temperatures.
About This Crystal
An opaque to translucent microcrystalline quartz specimen showing a mix of creamy chalcedony and reddish-brown carnelian patches. The surface appears rugged and unpolished with a waxy to dull luster on the matrix and a vitreous glint on small fractured silica faces.
Physical Characteristics
Color: Cream, tan, and reddish-brown; Streak: White; Cleavage: None; Fracture: Conchoidal to uneven; Specific Gravity: 2.58-2.64; Fluorescence: Inert to weak yellow-green under UV.
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: Up to 0.009; Pleochroism: None; Optical Character: Uniaxial positive (aggregate response); no significant dispersion.
Hardness & Durability
Origin Region
Commonly found in Brazil, India, Madagascar, and Uruguay; typically occurs in volcanic rock cavities or sedimentary gravels.
Hardness & Durability
Mohs Hardness: 6.5-7; Toughness: Very High due to its microcrystalline structure which resists fracturing and chipping better than macrocrystalline quartz.
Care & Maintenance
Clean with warm soapy water and a soft brush. Resistant to most household chemicals but should be kept away from hydrofluoric acid. Stable under sunlight but avoid extreme thermal shock.
Rarity & Value
Common; Value is determined by color saturation and translucency. In its raw matrix state, it is primarily a collector or lapidary rough material of modest value.
Special Characteristics
Often shows subtle banding (characteristic of agate) and contains iron oxide inclusions that provide the distinctive 'carnelian' reddish hue.
Lore & History
Historically used since the Neolithic for beads and seals. In Ancient Egypt, it was associated with the blood of Isis and used for protection. Traditionally believed in lore to enhance vitality and motivation.