sedimentary
Limestone Pebble
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3-4 (Mohs scale); Color: Gray to tan; Luster: Dull/Earthy; Crystal Structure: Trigonal (Microcrystalline); Cleavage: None visible in pebble form; Specific Gravity: 2.5-2.7
- Hardness
- 3-4 (Mohs scale)
- Color
- Gray to tan
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Gray to tan; Luster: Dull/Earthy; Crystal Structure: Trigonal (Microcrystalline); Cleavage: None visible in pebble form; Specific Gravity: 2.5-2.7
Formation & geological history
Limestone forms primarily in marine environments from the accumulation of coral, shell, algal, and fecal debris. It can also form through chemical precipitation from calcium-rich waters.
Uses & applications
Used extensively in construction (as aggregate or cement component), agriculture (soil treatment), and industrial glass manufacturing.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary component of most cave systems across the globe due to its solubility in acidic water.
Field identification & locations
Identify in the field by its softness (scratched by steel) and positive reaction (fizzing) to a 10% hydrochloric acid solution. Commonly found in riverbeds and ancient seafloors.
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