sedimentary
Limestone (Beach Pebble)
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3-4 (Mohs); Color: White to light grey; Luster: Dull or earthy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.7.
- Hardness
- 3-4 (Mohs)
- Color
- White to light grey
- Luster
- Dull or earthy
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Physical properties
Hardness: 3-4 (Mohs); Color: White to light grey; Luster: Dull or earthy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.7.
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. This specific specimen has been rounded and smoothed by water erosion/wave action.
Uses & applications
Primary source of lime for cement, used in construction as aggregate, and in the production of glass and steel. As a pebble, it is used in landscaping and aquariums.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains fossils that are too small to see without a microscope.
Field identification & locations
Identify in the field by its white/grey color and soft texture compared to quartz; it will react (fizz) when exposed to a weak acid like vinegar. Commonly found on beaches near chalk or limestone cliffs.
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