sedimentary
Limestone (River Pebble)
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3 (Mohs scale); Color: light gray to off-white; Luster: dull/earthy; Texture: fine-grained and smooth due to water erosion; Cleavage: none; Specific gravity: 2.5-2.7
- Hardness
- 3 (Mohs scale)
- Color
- light gray to off-white
- Luster
- dull/earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: light gray to off-white; Luster: dull/earthy; Texture: fine-grained and smooth due to water erosion; Cleavage: none; Specific gravity: 2.5-2.7
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments. This specific specimen has been further shaped by river or coastal erosion (abraded into a smooth pebble).
Uses & applications
Used in construction (aggregate), cement manufacturing, soil conditioning (lime), and as a common decorative garden stone.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary source of carbon for the global cycle and often contains micro-fossils not visible to the naked eye.
Field identification & locations
Identify in the field by its softness (can be scratched by a steel nail) and its reaction to dilute hydrochloric acid (it will fizz/effervesce). Look for it in riverbeds or coastal areas.
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