Carnelian Agate in Matrix
Quartz (var. Chalcedony) in Basaltic/Sedimentary Matrix · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal symmetry; Microcrystalline/Cryptocrystalline habit, typically massive or filling amygdaloidal cavities
Mineral Group
Silicates (Tectosilicate group, Quartz family)
Chemical Formula
SiO2 with Fe2O3 (Iron Oxide) inclusions
Formation Process
Hydrothermal or Sedimentary: Silica-rich fluids percolate through cavities (vesicles) in volcanic rock or sedimentary layers, depositing microcrystalline quartz over time
About This Crystal
The specimen features orange-to-reddish translucent patches of carnelian embedded within a dark, earthy, opaque grey-green matrix. The carnelian sections show a waxy to vitreous luster, while the matrix is dull to sub-vitreous. The texture is rough and irregular with visible pitting and fractures.
Physical Characteristics
Color: Orange-red (carnelian) and charcoal-grey (matrix); Streak: White; Cleavage: None; Fracture: Conchoidal (carnelian) to uneven (matrix); Specific Gravity: 2.58–2.64; Fluorescence: Typically inert or weak yellow-green under LWUV.
Optical Properties
Refractive Index: 1.530–1.540; Birefringence: Up to 0.004; Pleochroism: Absent; Optical Character: Uniaxial positive (aggregate response); Diaphaneity: Translucent (carnelian) to Opaque (matrix).
Hardness & Durability
Origin Region
Brazil, India, Uruguay, Madagascar, and various volcanic regions in the USA (e.g., Oregon, Washington) inside basalt or sedimentary hosts
Hardness & Durability
Mohs Hardness: 6.5–7; Toughness: High (carnelian is very durable due to its cryptocrystalline structure); Wearability: Excellent for jewelry when extracted from matrix.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid harsh chemicals and sudden temperature changes. Generally stable in sunlight, though some low-quality dyed material can fade.
Rarity & Value
Common; Value is generally low for raw specimens like this, though large, high-clarity nodules with vibrant color can command higher prices. Common treatments include heating to enhance red tones.
Special Characteristics
Features characteristic 'waxy' luster on fractured surfaces and color-zoning where iron oxide concentration varies. The bond between the carnelian and the host rock (matrix) is a distinct textural feature.
Lore & History
Historically used since the Neolithic era for beads and seals. In Ancient Egypt, it was associated with the blood of Isis and used for protection. Traditionally believed to enhance courage, vitality, and motivation (Sacral Chakra association).