sedimentary
Limestone (River Stone)
Calcite-rich Sedimentary Rock (CaCO3)
Hardness: 3 on Mohs scale; Color: Gray to buff with darker mottling; Luster: Dull/Earthy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal to uneven fracture); Specific Gravity: 2.3-2.7
- Hardness
- 3 on Mohs scale
- Color
- Gray to buff with darker mottling
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray to buff with darker mottling; Luster: Dull/Earthy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal to uneven fracture); Specific Gravity: 2.3-2.7
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments. This specific specimen has been rounded by fluvial (river) erosion over thousands of years.
Uses & applications
Used primarily in building construction, as an aggregate for road base, as a component of cement, and in the production of lime. Small water-worn specimens are common in landscaping.
Geological facts
Limestone accounts for about 10% of the total volume of all sedimentary rocks. It can often contain tiny fossils of marine organisms like crinoids or brachiopods.
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). Commonly found in riverbeds and ancient seafloor deposits.
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