sedimentary
Limestone (specifically fossiliferous/skeletal limestone)
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: typically light gray, tan, or off-white; Luster: dull to earthy; Structure: non-crystalline/granular; Cleavage: none (conchoidal fracture); Specific Gravity: 2.5-2.7
- Hardness
- 3 on Mohs scale
- Color
- typically light gray, tan, or off-white
- Luster
- dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: typically light gray, tan, or off-white; Luster: dull to earthy; Structure: non-crystalline/granular; Cleavage: none (conchoidal fracture); Specific Gravity: 2.5-2.7
Formation & geological history
Formed in warm, shallow marine environments through the accumulation of organic debris such as coral, shells, and algae. Over millions of years (often dating from the Paleozoic to the Cenozoic), these sediments undergo lithification under pressure.
Uses & applications
Broadly used in construction as aggregate, in the manufacture of cement and lime, as a soil conditioner in agriculture, and for building facades or sculptures.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. Most of the world's great pyramids and cathedrals are built from limestone due to its availability and ease of carving.
Field identification & locations
Identify in the field by applying a drop of cold 10% hydrochloric acid (vinegar can also work weakly), which will cause the stone to effervesce (fizz). Look for visible shell fragments or fossils. Found globally in areas that were once prehistoric seabeds.
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