sedimentary
Limestone Pebble
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Tan to light brown; Luster: Dull/earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.3-2.7
- Hardness
- 3 on Mohs scale
- Color
- Tan to light brown
- Luster
- Dull/earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Tan to light brown; Luster: Dull/earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.3-2.7
Formation & geological history
Formed by the accumulation of shell, coral, algal, and fecal debris in marine environments. Often dates from the Paleozoic or Mesozoic eras. This specimen shows signs of mechanical weathering and rounding by water transport.
Uses & applications
Used primarily in construction (crushed stone, cement), agriculture (soil conditioner), and as a chemical feedstock. Small pebbles such as this have low commercial value but are useful for educational purposes.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. Many limestones contain visible 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 effervescence when exposed to a weak acid like vinegar. Common in riverbeds and ancient seafloors.
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