sedimentary
Chert / Flint (Yellow Jasper Variant)
Microcrystalline Quartz (SiO2 with Iron Oxide impurities)
Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, mustard, ochre; Luster: Waxy to dull; Fracture: Distinct conchoidal fracture with sharp, curved edges; Specific gravity: 2.58-2.64
- Hardness
- 6
- Color
- Yellow-brown, mustard, ochre
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, mustard, ochre; Luster: Waxy to dull; Fracture: Distinct conchoidal fracture with sharp, curved edges; Specific gravity: 2.58-2.64
Formation & geological history
Formed through the accumulation and precipitation of silica-rich fluids within sedimentary rock layers like limestone or chalk. Iron oxides like goethite or limonite give it its characteristic yellow-brown coloration.
Uses & applications
Historically used for knapping stone tools, arrowheads, and fire-starting (spark generation). Today used for lapidary arts, landscaping, cabochons, and mineral collecting.
Geological facts
Due to its smooth conchoidal fracture, chert and flint were among the very first raw materials used by early humans during the Stone Age to produce cutting tools and weapons.
Field identification & locations
Look for a smooth, waxy surface with sharp, shell-like (conchoidal) fractures that readily scratch glass. Commonly found in riverbeds, gravel deposits, and limestone outcrops globally.
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