Oolitic Limestone: is composed mainly of calcium carbonate “oolites,” small spheres formed by the concentric precipitation of calcium carbonate on a sand grain or shell fragment.Lithographic Limestone : A dense limestone with a uniform grain size which is a very smooth surface.Fossiliferous Limestone: contains abundant fossils, normally shell and skeletal fossils of the organisms.Coquina: It is composed mainly of broken shell debris, formed on beaches where wave action fragment shells.It is formed usually from the calcareous shell remains of microscopic marine organisms. Chalk: A soft limestone with fine texture, generally white or light grey.These names are based upon how the rock formed, its appearance, and its composition. There are many different names used for limestone. If the droplet falls to the floor and evaporates there, it forms stalagmites that could grow upwards from the cave floor. Over time, this evaporative process can result in an accumulation of icicle-shaped calcium carbonate on the cave ceiling that forms stalactites. There they might evaporate before falling to the cave floor. In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. Stalactites, stalagmites, and other cave formations (often called “ speleothems “) are examples of limestone formed through evaporation. Limestone can also form through evaporation. Payne Limestone, Lower Mississippian Lake Cumberland, Kentucky, USA) These deposits sometimes grow to several hundred miles in length.Įncrinite (crinoidal limestone) (Ft. Reef-like Limestones and Shell Limestones: These limestones contain the remains of corals, brachiopods, clams, oysters, bryozoans, and other forms.These small animals, whose shells look like wheat grains, formed these kinds of limestones. Fusilinid Limestones: Fusilinid is one of the single-celled animals called Foraminifera.These are found extensively in eastern Kansas and Pennsylvania. The stems break into small, disc-shaped fragments. Crinoidal Limestones: Crinoids are sea animals that had long stems, cup-like bodies that look like flowers, and for this reason, called sea lilies.When the organisms die, their shells are left on the ocean floor, lake bottom, or river bed where they accumulate into deposits.Įarth has many limestone-forming settings: most of them are found in shallow water, for example in the Caribbean Sea, Indian Ocean, Persian Gulf, Gulf of Mexico, and around Pacific Ocean islands. Most limestones come from marine deposits, but some are formed in lakes, rivers, and on land. It can be formed in two ways: by the accumulation of living organisms and by evaporation. Therefore, its color is influenced by sediments in the mixture. Because it is often formed from shells or bones, it has a light tone color like white, tan, or grey. However, it can also be formed by the precipitation of calcium carbonate from lake or ocean water. It usually forms in clear, warm, shallow marine waters from the accumulation of shell, coral, algal, and fecal debris. Its origins can be traced back to either chemical or biochemical processes that occurred in the past (hundreds of millions of years ago). Limestone is a sedimentary rock consisting of 50% of calcium carbonate (CaCO3) in the mineral calcite form. Sedimentary rocks are important because they often contain fossils that give us indications about past ages. Limestone is a sedimentary rock, formed from small pressurized particles of rocks and stones.
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