Chert
Mineral NameChert
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemamorphous
Lusterwaxy
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.6
Colorsgray, brown, black, white, red, green
Transparencyopaque
Type LocalityWidespread in sedimentary formations globally
Mineral GroupSilicates
Usesflintknapping, tools, building material, road aggregate
Associated Mineralscalcite, dolomite, clay minerals, iron oxides
Raritycommon
Description
This image shows a gray, irregularly shaped piece of chert, exhibiting characteristic sharp edges and conchoidal fractures from being broken or worked.
Geological Context
Chert is a fine-grained sedimentary rock composed of microcrystalline quartz, commonly forming as nodules or beds within limestone or dolomite through the replacement of carbonate minerals or direct precipitation from silica-rich waters.
