sedimentary
Limestone (River Pebble)
Calcite-rich Sedimentary Rock (CaCO3)
Hardness: 3-4 Mohs; Color: Light gray to white; Luster: Dull/Earthy; Crystal structure: Microcrystalline (trigonal); Cleavage: None visible in pebble form; Specific gravity: 2.3-2.7
- Hardness
- 3-4 Mohs
- Color
- Light gray to white
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 Mohs; Color: Light gray to white; Luster: Dull/Earthy; Crystal structure: Microcrystalline (trigonal); Cleavage: None visible in pebble form; Specific gravity: 2.3-2.7
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments; followed by lithification over millions of years and eventual smoothing by water erosion (river or beach action).
Uses & applications
Mainly used in construction as aggregate, in cement manufacturing, as a soil conditioner in agriculture, and as a raw material in the chemical industry.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in famous landscapes like the Grand Canyon and the karst towers of Vietnam.
Field identification & locations
Identify by its light color and reaction (fizzing) when exposed to a weak acid like vinegar. Commonly found in riverbeds, lakeshores, and coastal areas where ancient sea beds are exposed.
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