sedimentary
Limestone (specifically Grainstone or Micrite)
Calcium Carbonate (CaCO3)
Hardness: 3 (Mohs scale); Color: ranges from grey to tan/white; Luster: dull to earthy; Structure: non-crystalline fine-grained matrix; Specific Gravity: 2.3-2.7
- Hardness
- 3 (Mohs scale)
- Color
- ranges from grey to tan/white
- Luster
- dull to earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: ranges from grey to tan/white; Luster: dull to earthy; Structure: non-crystalline fine-grained matrix; Specific Gravity: 2.3-2.7
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. This specific river-tumbled specimen likely originates from Paleozoic or Mesozoic era deposits.
Uses & applications
Used primarily in construction as aggregate for concrete, road base, and as a raw material for cement or agricultural lime.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains microscopic fossils and is the primary rock type found in karst landscapes (caves and sinkholes).
Field identification & locations
Identify in the field by its softness (can be scratched by a steel nail) and its effervescent reaction to a weak acid like vinegar. Commonly found in riverbeds within sedimentary basins.
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