sedimentary
Limestone (with Chert)
Calcium Carbonate (CaCO3) / Microcrystalline Quartz (SiO2)
Hardness 3 (limestone matrix) to 7 (chert inclusions) on Mohs scale; dark gray to brownish-buff color; dull to earthy luster; fine-grained microcrystalline structure; reactive to dilute acid on limestone parts.
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Physical properties
Hardness 3 (limestone matrix) to 7 (chert inclusions) on Mohs scale; dark gray to brownish-buff color; dull to earthy luster; fine-grained microcrystalline structure; reactive to dilute acid on limestone parts.
Formation & geological history
Formed in shallow marine environments by the accumulation of organic debris like shells, coral, and algal remains, often with silica precipitating to form embedded chert nodular bands.
Uses & applications
Commonly used in construction aggregate, cement manufacturing, lime production, soil conditioning, and geological study specimens.
Geological facts
Limestone forms huge karst landscapes around the world including caves and sinkholes. It often contains abundant microfossils.
Field identification & locations
Identified in the field by effervescing (fissing) when exposed to cold dilute hydrochloric acid and by its fine-grained gray texture. Found in sedimentary basins worldwide.
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