sedimentary
Limestone Nodule
Sedimentary limestone concretion, primarily CaCO3
AI-generated identification · may be incorrectHardness 3 on Mohs scale, typically off-white to gray in color with a dull to earthy luster, cryptocrystalline structure, and exhibits effervescence when exposed to dilute hydrochloric acid.
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Physical properties
Hardness 3 on Mohs scale, typically off-white to gray in color with a dull to earthy luster, cryptocrystalline structure, and exhibits effervescence when exposed to dilute hydrochloric acid.
Formation & geological history
Formed through the chemical precipitation of calcium carbonate and accumulation of marine skeletal fragments in ancient shallow marine environments over millions of years.
Uses & applications
Used primarily in aggregate, cement production, soil conditioning, and occasionally collected as geological specimens.
Geological facts
Limestone nodules often form around a nucleus like a shell or fossil fragment, growing concentrically within soft sediment layers.
Field identification & locations
Easily identified by its reaction to acid and soft relative hardness; commonly found in sedimentary strata worldwide, particularly in regions with past marine coverage.
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