sedimentary
Chert
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, waxy to dull luster, conchoidal fracture, crypto-crystalline structure, specific gravity around 2.60.
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Physical properties
Hardness of 7 on the Mohs scale, waxy to dull luster, conchoidal fracture, crypto-crystalline structure, specific gravity around 2.60.
Formation & geological history
Forms by the replacement of calcium carbonate by silica in marine environments or through the accumulation of siliceous skeletal remains of microscopic organisms over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-strike implements due to its sharp conchoidal fracture.
Geological facts
Also commonly known as flint when found in chalk deposits. It is exceptionally durable and resistant to weathering.
Field identification & locations
Easily identifiable in the field by its distinct waxy luster and sharp, curved conchoidal fracture edges. Found worldwide in sedimentary rock sequences.
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