sedimentary
Chert (Flint/Jasper)
Microcrystalline Quartz (SiO2)
Mohs hardness of 7. Dull to waxy luster, microcrystalline structure, conchoidal fracture. Color ranges from buff-tan and yellowish-brown to dark gray/black with iron oxide staining.
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Physical properties
Mohs hardness of 7. Dull to waxy luster, microcrystalline structure, conchoidal fracture. Color ranges from buff-tan and yellowish-brown to dark gray/black with iron oxide staining.
Formation & geological history
Formed in sedimentary marine or lacustrine environments from the precipitation of silica-rich solutions or biological accumulation of siliceous organism remains (such as radiolarians or diatoms).
Uses & applications
Historically used for making stone tools, arrowheads, and spark-striking flints. Modernly used in road construction aggregate, landscaping, and lapidary art.
Geological facts
Chert was one of the most important raw materials for prehistoric humans due to its ability to break with razor-sharp conchoidal edges.
Field identification & locations
Identified by its extreme hardness (scratches glass readily), smooth to slightly waxy texture on fresh surfaces, sharp fractured edges, and resistance to weathering. Highly abundant worldwide in limestone and chalk formations.
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