sedimentary
Coquina
Biogenic Limestone (Calcium Carbonate, CaCO3)
AI-generated identification · may be incorrectHardness: 2-3 (Mohs scale); Color: Tan, brownish, or gray; Luster: Dull/Earthy; Structure: Clastic fossil fragments; Porosity: Very high.
- Hardness
- 2-3 (Mohs scale)
- Color
- Tan, brownish, or gray
- Luster
- Dull/Earthy
Identified More sedimentary →
Explore Coquina in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 2-3 (Mohs scale); Color: Tan, brownish, or gray; Luster: Dull/Earthy; Structure: Clastic fossil fragments; Porosity: Very high.
Formation & geological history
Formed in high-energy marine environments (beaches or barrier islands) where shells are broken by wave action and later cemented together by calcium carbonate.
Uses & applications
Historically used as a building material for forts and homes due to its ability to absorb cannon fire (it compresses rather than shattering). Used today as road base or landscaping stone.
Geological facts
The Castillo de San Marcos in Florida was built of coquina; during battles, cannonballs would sink into the soft stone rather than breaking it.
Field identification & locations
Identify by looking for a mass of visible, broken shell fragments. It will react and fizz strongly when exposed to dilute hydrochloric acid (vinegar).
More like this
Other sedimentary specimens
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary