sedimentary
Gray Limestone
Carbonate rock (CaCO3)
Hardness: 3 (Mohs scale), Color: Medium to light gray, Luster: Dull to earthy, Structure: Fine-grained/microcrystalline, Cleavage: None/Chunky
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Physical properties
Hardness: 3 (Mohs scale), Color: Medium to light gray, Luster: Dull to earthy, Structure: Fine-grained/microcrystalline, Cleavage: None/Chunky
Formation & geological history
Formed by the accumulation of shell, coral, algal, and fecal debris in marine environments. This specimen appears to be a weather-worn clast, likely from the Paleozoic or Mesozoic era.
Uses & applications
Limestone is used extensively in construction, as road base, in the production of cement/concrete, and in the chemical industry for neutralization of acidity.
Geological facts
Limestone accounts for about 10% of the total volume of all sedimentary rocks. It is the primary source of lime used in agriculture to adjust soil pH.
Field identification & locations
Can be identified in the field by its softness compared to quartz (can be scratched by a steel nail) and its effervescence (bubbling) when a drop of dilute hydrochloric acid is applied.
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