sedimentary

Limestone Pebble

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

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

Identified July 4, 2026More sedimentary →

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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.