sedimentary
Chert / Flint
Microcrystalline Quartz (SiO2)
Hardness 7 on Mohs scale; color ranges from off-white, light gray, yellowish to beige; dull to waxy or vitreous luster; microcrystalline or cryptocrystalline structure; conchoidal fracture with sharp edges; specific gravity around 2.65.
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Physical properties
Hardness 7 on Mohs scale; color ranges from off-white, light gray, yellowish to beige; dull to waxy or vitreous luster; microcrystalline or cryptocrystalline structure; conchoidal fracture with sharp edges; specific gravity around 2.65.
Formation & geological history
Formed through the accumulation of silica-rich biogenic sediments (such as radiolarian or diatom oozes) or precipitation of silica in groundwater within limestone and chalk beds during diagenesis.
Uses & applications
Historically used for stone tools, arrowheads, and spark-striking flints; modernly used as road aggregate, raw material for silica, and as lapidary rough or educational specimens.
Geological facts
Chert and flint were among the earliest raw materials utilized by prehistoric humans to craft sharp-edged knapped tools due to its characteristic conchoidal fracturing.
Field identification & locations
Identified in the field by its hardness (scratches steel/glass easily), smooth to waxy feel on fresh surfaces, and characteristic curved, shell-like (conchoidal) fractures; common in sedimentary rock formations, especially limestone outcrops.
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