sedimentary

Limestone (specifically Grainstone or Micrite)

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

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

Identified April 12, 2026More sedimentary →

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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.