Chert (specifically Red Chert or Jasper-like Chert)
Microcrystalline Quartz (Silicon Dioxide) · Mineral Specimen / Decorative Stone
Crystal System
Trigonal (Microcrystalline/Cryptocrystalline); Habit: Massive, lacking visible crystal faces, occurring as nodules or bedded deposits.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 with trace Iron Oxide (Fe2O3) impurities causing the reddish-brown coloration.
Formation Process
Sedimentary/Hydrothermal; forms via chemical precipitation of silica-rich fluids in deep marine environments or by the replacement of carbonate material (limestone/dolomite) at low temperatures and pressures.
About This Crystal
A dense, opaque to slightly translucent reddish-brown mass. It exhibits a waxy to dull luster and a characteristic conchoidal fracture (curved, shell-like breaks) visible on the fresh surface. The exterior has a roughened, earthy texture indicative of weathering.
Physical Characteristics
Color: Brownish-red to tan; Streak: White; Cleavage: None; Fracture: Prominent conchoidal; Specific Gravity: 2.58–2.64; Tenacity: Brittle; Fluorescence: Generally inert.
Optical Properties
Refractive Index: ~1.544–1.553; Birefringence: Low to none visible (aggregates); Non-pleochroic; Singly refractive in aggregate form.
Hardness & Durability
Origin Region
Globally abundant; notable for occuring in sedimentary basins, marine limestone formations (e.g., USA, UK, China, and Australia) and river gravels.
Hardness & Durability
Mohs Hardness: 6.5–7; Toughness: Very high due to interlocking micro-structure; Stability: Excellent, resistant to most acids except Hydrofluoric.
Care & Maintenance
Safe to clean with warm soapy water and soft brushes. Avoid ultrasonic cleaners if fractures are present. Resistant to fading; store separately from softer minerals like calcite.
Rarity & Value
Common; Rarity: Low; Value Factors: Color patterns and size; typically inexpensive ($1–$10 for small specimens) unless shaped into artifacts or highly polished.
Special Characteristics
Characterized by its ability to produce sparks when struck against steel (fire-starting capability) and its historic use in flintknapping to create sharp edges.
Lore & History
Historically significant as the primary material for stone age tools, arrowheads, and scrapers due to its predictable fracture patterns. In traditional lore, it is considered a stone of grounding, endurance, and protection, often associated with the Root Chakra.