sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3-4 (Mohs scale); Color: Gray, tan, or white; Luster: Dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.7.
- Hardness
- 3-4 (Mohs scale)
- Color
- Gray, tan, or white
- Luster
- Dull to earthy
Identified More sedimentary →
Explore Limestone in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3-4 (Mohs scale); Color: Gray, tan, or white; Luster: Dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.7.
Formation & geological history
Formed in marine environments through the accumulation of shell, coral, algal, and fecal debris. It can also form via precipitation of calcium carbonate from lake or ocean water.
Uses & applications
Used primarily as raw material for cement, building stone, aggregate for road bases, and as a flux in steel manufacturing. It is also ground for agricultural use.
Geological facts
Limestone covers about 10% of the Earth's land surface. It is often the primary component of caves and karst landscapes due to its solubility in weak acids.
Field identification & locations
Identify in the field by applying a drop of dilute hydrochloric acid; it will effervesce (fizz). Look for visible fossils or shell fragments. Commonly found in large deposits across the Midwestern USA and Europe.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary