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1. (Limestone Rock) University of Zakho College of Basic Education Dept. of general science 3 rd Stage (2022-2023) Prepared by: Ahmed Haji Bahzad Nayf Sarmand Sulieman Supervisor : Dr . Ramazan

2. Lest of Contents What Is Limestone? Biological Limestones Chemical Limestones Limestone-Forming Environments Evaporative Limestones Composition of Limestone Types of Limestone Uses of Limestone Q uick lime stone Slaked lime stone references

3. What Is Limestone? Limestone is a sedimentary rock composed primarily of calcite, a calcium carbonate mineral with a chemical composition of CaCO3. It usually forms in clear, calm, warm, shallow marine waters. It can also form by chemical sedimentary processes, such as the precipitation of calcium carbonate from lake or ocean water

4. Biological Limestones Most limestones form in calm, clear, warm, shallow marine waters. That type of environment is where organisms capable of forming calcium carbonate shells and skeletons can thrive and easily extract the needed ingredients from ocean water. When these animals die, their shell and skeletal debris accumulate as a sediment that might be lithified into limestone. Their waste products also contribute to the sediment mass. Limestones formed from this type of sediment are biological sedimentary rocks. Their biological origin is often, but not always, revealed in the rock by the presence of  fossils .

5. Chemical Limestones Some limestones form by direct precipitation of calcium carbonate from marine or fresh water. Limestones formed this way are chemical sedimentary rocks. They are thought to be less abundant than biological limestones . Most biological limestones contain significant amounts of directly precipitated calcium carbonate. After the biological grains have accumulated and are buried, water that is saturated with dissolved materials moves slowly through the sediment mass. Calcium carbonate, precipitated directly from solution, forms as a "cement" that binds the biological grains together.

6. Limestone-Forming Environments Many limestone-forming environments are active on Earth today. Most of them are found in shallow parts of the ocean between 30 degrees north latitude and 30 degrees south latitude. Limestone is forming in the  Caribbean Sea , Indian Ocean, Persian Gulf, Gulf of Mexico, around Pacific Ocean islands, and within the  Indonesian archipelago .

7. Evaporative Limestones Limestone can also form through evaporation. Stalactites, stalagmites, and other cave formations (often called "speleothems") are examples of limestone that formed through evaporation. In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. There they might evaporate before falling to the cave floor. When the water evaporates, any calcium carbonate that was dissolved in the water will be deposited. Over time, this evaporative process can result in an accumulation of icicle-shaped calcium carbonate on the cave ceiling.

8. These features are known as stalactites

9. Types of Limestone Chalk Crystalline Limestone Lithographic Limestone Dolomitic Limestone Fossiliferous Limestone

10. Uses of Limestone Limestone  is a rock with a diversity of uses. It could be the one rock that is used in more ways than any other. Most limestone is made into  crushed stone  that is used in road base, railroad ballast, foundation stone, drainfields , concrete aggregate, and other construction uses. It is fired in a kiln with crushed shale to make cement.

11. References Allen TFM (1971) Multivariate approaches to the ecology of algae on terrestrial rock surfaces in North Wales. J Ecol 59: 803-826. Al-Thukair AA and Golubic S (1991) New endolithic cyanobacteria from the Arabian Gulf. 1. Hyella immanis sp. nov. J Phycol 27: 766-780. Anagnostidis K, Economou-Amilli A and Roussomoustakaki M (1983) Epilithic and chasmolithic microflora (Cyanophyta, Bacillariophyta) from marbles of the Parthenon (Acropolis, Athens, Greece). Nova Hedwigia 38: 227-281. Arp G and Reitner J (1998) Cyanobacteria in calcifying biofilms of alkaline salt lakes. Abstracts, Cyanobacteria in Action in the Lithosphere and in the Biosphere. 12 International Senckenberg Conference, November 16-19, 1998, Frankfurt, Germany.