sedimentary

Limestone (specifically Marl or Chalk)

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: White, light gray; Luster: Dull/Earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (in bulk form); Specific Gravity: 2.3–2.7

Hardness: 3 (Mohs scale)
Color: White, light gray
Luster: Dull/Earthy

Identified April 17, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: White, light gray; Luster: Dull/Earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (in bulk form); Specific Gravity: 2.3–2.7

Formation & geological history

Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments. This specific crumbly white specimen suggests a biological origin from marine microorganisms.

Uses & applications

Primarily used in construction (as aggregate), cement manufacturing, soil conditioning in agriculture, and as a precursor for quicklime.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is essential for the formation of cave systems through the process of chemical weathering by slightly acidic rainwater.

Field identification & locations

Identify in the field by its softness (can be scratched by a copper coin) and its energetic effervescence (bubbling) when a drop of weak acid like vinegar is applied. Commonly found in road beds as crushed gravel.