sedimentary

Chert (potentially Flint or Mudstone)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Dark brown to black; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.

Hardness: 7 on Mohs scale
Color: Dark brown to black
Luster: Waxy to dull

Identified May 8, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Dark brown to black; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.

Formation & geological history

Formed via the accumulation of siliceous remains of organisms (like diatoms) or chemical precipitation from groundwater. Common in limestone and chalk deposits dating back to various geological periods.

Uses & applications

Historically used for stone tools and weapons (arrowheads). Today used as a decorative stone, in construction aggregate, and by survivalists for fire-starting.

Geological facts

Flint is a variety of chert that was the first 'high-tech' material for humans, used to create razor-sharp edges and sparks for fire. Small specimens are often found in riverbeds or within limestone outcrops.

Field identification & locations

Identify by its conchoidal (shell-like) fracture patterns and ability to scratch glass. It is often found as nodules or layers within sedimentary rock formations.