sedimentary
Chert
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, typically grey, brown, or black with a waxy to dull luster, conchoidal fracture, and no cleavage.
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Physical properties
Hardness of 7 on the Mohs scale, typically grey, brown, or black with a waxy to dull luster, conchoidal fracture, and no cleavage.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions or the accumulation of siliceous skeletal remains of marine organisms over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-producing fire starters; currently used in aggregate and abrasives.
Geological facts
Chert was one of the earliest materials utilized by humans for knapping cutting tools and weapons due to its sharp conchoidal fracture.
Field identification & locations
Can be identified in the field by its hardness (scratches glass), waxy luster, and distinctive conchoidal fracture patterns.
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