sedimentary
Chert / Flint (River Pebble)
Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Cream, tan, gray; Luster: Waxy to dull; Crystal structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Cream, tan, gray
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Cream, tan, gray; Luster: Waxy to dull; Crystal structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary environments. This specimen shows significant rounding and smoothing likely caused by fluvial (river) or coastal erosion processes.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to its sharp edges; currently used in construction aggregate, road surfacing, and as landscaping stone.
Geological facts
Flint is a variety of chert that has been used by humans for hundreds of thousands of years to create fire (by striking against steel) and high-quality tools. It is one of the toughest common rocks found in nature.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and smooth, water-worn texture. Commonly found in riverbeds, gravel pits, and coastal beaches globally. Collectors look for unique shapes or colors.
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