sedimentary
Jasper / Chert (Iron-stained Quartz)
SiO2 (Silicon Dioxide with Iron Oxide inclusions)
Hardness: 6.5-7 on the Mohs scale. Color: Reddish-brown, orange-tan, ochre. Luster: Earthy, dull to sub-vitreous. Cleavage: None (conchoidal fracture). Specific Gravity: ~2.6-2.65.
- Hardness
- 6
- Color
- Reddish-brown, orange-tan, ochre
- Luster
- Earthy, dull to sub-vitreous
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Physical properties
Hardness: 6.5-7 on the Mohs scale. Color: Reddish-brown, orange-tan, ochre. Luster: Earthy, dull to sub-vitreous. Cleavage: None (conchoidal fracture). Specific Gravity: ~2.6-2.65.
Formation & geological history
Formed via chemical precipitation of microcrystalline quartz in sedimentary environments or low-grade metamorphism, heavily stained by secondary iron oxides (hematite/goethite).
Uses & applications
Used primarily for landscaping, decorative stone, tumbled specimens, lapidary cabochons, and historically for flintknapping primitive tools.
Geological facts
Iron-rich jasper and chert are among the most widespread microcrystalline quartz varieties on Earth. Red and brown hues are directly caused by hydrated iron oxides.
Field identification & locations
Look for a smooth, waxy to earthy texture, high hardness (scratches glass, cannot be scratched by a steel pocketknife), and distinct reddish-orange to brown iron staining. Common in stream beds, gravel pits, and sedimentary rock outcrops.
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