sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs), Color: Dark brown to black, Luster: Waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs), Color: Dark brown to black, Luster: Waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Forms through the accumulation of siliceous remains of marine organisms or by precipitation of silica in groundwater. Often found in limestone or chalk deposits.
Uses & applications
Historically used for stone tools and starting fires; currently used in construction as aggregate and in jewelry as a gemstone.
Geological facts
Flint was crucial for prehistoric technological advancement, particularly in tool making. It sparks when struck against steel due to its hardness and iron impurities.
Field identification & locations
Identify by its smooth, waxy surface and sharp, curved (conchoidal) edges when broken. Commonly found in riverbeds, chalk cliffs, and sediment.
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