sedimentary

Chert / Flint

Cryptocrystalline Quartz (Silicon Dioxide, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Variegated grays, blues, and browns as seen in the specimen; Luster: Waxy to dull; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Variegated grays, blues, and browns as seen in the specimen
Luster: Waxy to dull

Identified March 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments. Often found as nodules within limestone or chalk beds. Formation can span from the Precambrian to recent geological eras.

Uses & applications

Historically used for stone tools and starting fires; currently used as a raw material in ceramics, road construction (aggregate), and occasionally as semi-precious gemstones for lapidary work.

Geological facts

Due to its conchoidal fracture, it breaks into razor-sharp edges, making it the primary material for prehistoric arrowheads and spear points. It is often referred to as 'flint' if it occurs in chalk or high-quality dark nodules.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its smooth, curved (conchoidal) breakage surfaces. It is commonly found in riverbeds or weathered out of sedimentary bedrock. Tips: look for the 'waxy' texture compared to surrounding rock.