sedimentary
Limestone
CaCO3 (principally Calcite)
Hardness: 3 (Mohs scale), Color: tan to gray, Luster: dull/earthy, Crystal structure: Trigonal (as calcite), reacts with dilute HCl acid, specific gravity: 2.3-2.7
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Physical properties
Hardness: 3 (Mohs scale), Color: tan to gray, Luster: dull/earthy, Crystal structure: Trigonal (as calcite), reacts with dilute HCl acid, specific gravity: 2.3-2.7
Formation & geological history
Formed through the accumulation of shell, coral, algal and fecal debris in marine environments; age varies depending on the specific deposit (often Paleozoic or Mesozoic)
Uses & applications
Used extensively in construction (aggregate, cement), agriculture (lime), and industrial processes like steel manufacturing
Geological facts
Limestone covers about 10% of the Earth's total land surface. It is the primary rock type found in famous landscapes like the Grand Canyon walls and the chalk cliffs of Dover
Field identification & locations
Identify by testing with a drop of vinegar or weak acid (it will fizz). Commonly found in areas with ancient seabeds; collectors look for fossil inclusions
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