sedimentary

Chert / Flint (with Jasper inclusions)

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale. Color: Cream, tan, yellowish-brown, and dark reddish-brown inclusions. Luster: Waxy to dull. Crystal structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (exhibits conchoidal to subconchoidal fracture). Specific gravity: 2.6-2.7.

Hardness: 7 on Mohs scale
Luster: Waxy to dull

Identified July 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily in marine sedimentary environments through the precipitation of silica-rich fluids or the accumulation of siliceous biogenic remains (diatoms, radiolarians). Over time, compaction and recrystallization convert the silica into microcrystalline quartz.

Uses & applications

Historically used for stone tools, arrowheads, and spark-striking flintlocks. Currently used in landscaping, as aggregate in road construction, and occasionally for lapidary work or polishing by collectors.

Geological facts

Chert and flint are among the oldest materials used by early humans to manufacture sharp-edged tools due to their predictable conchoidal fracture pattern.

Field identification & locations

Identified in the field by its high hardness (scratches glass), waxy luster, smooth surface texture, and smooth curved fractures. Commonly found in limestone, chalk beds, gravel deposits, and river beds worldwide.

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