sedimentary
Chert / Flint
Microcrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale; color varies from olive green, gray, brown, to yellowish; waxy to vitreous luster; cryptocrystalline or microcrystalline structure; conchoidal fracture with no true cleavage; specific gravity around 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; color varies from olive green, gray, brown, to yellowish; waxy to vitreous luster; cryptocrystalline or microcrystalline structure; conchoidal fracture with no true cleavage; specific gravity around 2.60 to 2.65.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions or the replacement of calcium carbonate in limestone by silica-rich groundwater during diagenesis.
Uses & applications
Historically used for making stone tools, arrowheads, and spark generation in firearms; modern uses include aggregate, landscaping, and lapidary art.
Geological facts
Chert and flint are chemically identical, both being microcrystalline quartz, though 'flint' is often reserved for dark or black varieties found in chalk.
Field identification & locations
Easily identified by its smooth, conchoidal fracture and high hardness (scratches glass); found globally within sedimentary limestone and chalk formations.
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