Agatized Jasper / Chert
Silicon Dioxide (Microcrystalline Quartz) · Semi-Precious Gemstone / Lapidary Material
Crystal System
Trigonal (Hexagonal) system; microcrystalline/cryptocrystalline habit that is massive and non-granular.
Mineral Group
Silicates (Tectosilicate group, Quartz family)
Chemical Formula
SiO2 with Fe2O3 (Hematite) and various mineral impurities
Formation Process
Sedimentary or Hydrothermal; formed from silica-rich fluids precipitating in rock cavities or replacing organic matter at low temperatures/pressures.
About This Crystal
An opaque, earthy red to brown host rock (Jasper) featuring translucent to white bands or pockets of Chalcedony (Agate). Luster is dull to waxy, becoming vitreous when wet or polished.
Physical Characteristics
Color: Ocher-red, brown, and milky white; Streak: White; Cleavage: None; Fracture: Conchoidal to splintery; Specific Gravity: 2.58–2.91; Fluorescence: Often inert, but may show dull green or white under SW-UV.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: Weak (0.009); Optical Character: Uniaxial positive; Opaque to translucent appearance.
Hardness & Durability
Origin Region
Common worldwide; notably found in riverbeds and volcanic deposits in the Western United States, Brazil, and India.
Hardness & Durability
Mohs Hardness: 6.5–7; highly durable and tough for jewelry use; resistant to most household chemicals.
Care & Maintenance
Clean with warm soapy water and a soft brush; safe for ultrasonic cleaning; avoid hydrofluoric acid; stable in sunlight.
Rarity & Value
Common; value depends on pattern and color saturation. Typically $1–$20 per pound for rough material, higher for polished specimens.
Special Characteristics
Displays 'vug' or vein fillings of chalcedony within a ferruginous jasper matrix; features brecciated patterns and iron-oxide staining.
Lore & History
Historically used for tools and amulets in ancient Egypt and Mesopotamia; traditionally associated with grounding, protection, and physical strength in lore.