sedimentary
Chert (Chalcedony/Agate Pebble)
Cryptocrystalline Silica (SiO2)
Hardness: 6.5-7 (Mohs); Color: Waxy brown, honey-toned, and translucent; Luster: Waxy to vitreous; Structure: Microcrystalline; Conchoidal fracture common.
- Hardness
- 6
- Color
- Waxy brown, honey-toned, and translucent
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Waxy brown, honey-toned, and translucent; Luster: Waxy to vitreous; Structure: Microcrystalline; Conchoidal fracture common.
Formation & geological history
Formed through the precipitation of silica from groundwater in sedimentary host rocks or as a replacement of organic material. These water-worn pebbles are often found in riverbeds or glacial deposits.
Uses & applications
Commonly used in tumbled stones, decorative landscaping, and historically for stone tools due to its sharp-edged fracture; occasionally used in lapidary work.
Geological facts
Flint is a variety of chert. This specific specimen shows characteristic waxy luster and translucency typical of creek-worn chalcedony.
Field identification & locations
Identify in the field by its waxy appearance, smooth water-worn surface, and inability to be scratched by a steel knife. Common in gravel pits and beaches worldwide.
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