sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Tan, beige, or gray; Luster: Dull/Earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals, though often inconspicuous in rock form.
- Hardness
- 3 on Mohs scale
- Color
- Tan, beige, or gray
- Luster
- Dull/Earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3 on Mohs scale; Color: Tan, beige, or gray; Luster: Dull/Earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals, though often inconspicuous in rock form.
Formation & geological history
Formed primarily in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from calcium-rich waters.
Uses & applications
Used extensively in construction as road base, concrete aggregate, and building stone. Also used in the production of lime, cement, and as a soil conditioner in agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. Most of the world's caves are formed in limestone because it is easily dissolved by slightly acidic groundwater.
Field identification & locations
Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (bubbling) when in contact with dilute hydrochloric acid or strong vinegar. Common in karst landscapes and coastal cliffs.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary