Limestone: Definition, Formation Process, and Types

Limestone is a sedimentary rock composed of CaCO3 (calcium carbonate) in the form of calcite minerals. In general, limestone is formed from the accumulation of corals, shells, fragments of the rest of organisms, and algae. This limestone can also be categorized as chemical sedimentary rock because the formation process occurs due to the deposition of calcium carbonate from sea water or lake water. Therefore, this type of stone is very easy to find in shallow water areas.

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Definition of Limestone / Lime

In principle, limestone is a type of rock that contains about 50% by weight of calcium carbonate in the form of calcite minerals. While the remaining content in it consists of various minerals such as clay, quartz, siderite, pyrite, feldspar, and various other minerals.

The content of calcium carbonate found in limestone is one of the physical characteristics that are often used in identifying this type of rock. Usually, in the process of identifying limestone is done by dripping 5% HCl (hydrochloric acid). If the stone experiences a reaction, it can be ascertained that the rock is limestone.

Limestone / Lime Formation Process in the Marine Environment

Most limestone is formed in large areas with calm currents and in waters that have warm conditions. This is the most suitable environment so that organisms in the water can form dead skeletons and calcium carbonate shells which are the main sources of limestone formation. So when the organisms die, their skeletons and shells will accumulate to form sediments which will later undergo a process that becomes limestone.

Residual products from these organisms also have a considerable contribution in the formation of sediment mass. This is because there are limestone formed from the remaining sediments of the organism. Limestone, this type is categorized as biological sedimentary rock.

Some types of limestone can also be formed by deposition of calcium carbonate directly from seawater. The process of forming limestone like this is categorized as chemical sedimentary rock. It's just that the amount of limestone in the chemical sediment category is very small when compared to biological limestone.

Limestone / Lime Formation Process in Evaporation Environment

In addition to the above process, limestone or limestone can also be formed from the evaporation process. The example of limestone from the evaporation process is stalagmite, stalactite, and other rocks found in caves with high humidity. So in the cave, water droplets or seepage from above will enter the cave through cracks or pores in the sky. After that, the water undergoes an evaporation process before falling to the cave floor. From this very long process, finally limestone is formed.

When the water evaporates, all the calcium carbonate that is released in the water will be stored in the ceiling of the cave. Over time, the evaporation process will accumulate and eventually form a stalactite or cave rock that protrudes downward. Whereas when the water droplets inside the cave fall to the floor and eventually evaporate and grow upwards, they are called stalagmites or cave rocks that stand upwards.

Types of Limestone

Actually there are many names that are used to indicate limestone. These names are based on how the rock is formed, the texture, the composition of the minerals that make up the rock, and various other factors. From that process, various types of limestone appear. The explanation is as follows:

Chalk

It is a limestone that has a smooth texture and is very soft to the touch. This limestone generally has the color gray or white. The chalk formation process comes from calcareous shells from microscopic marine organisms such as seaweed or foraminifera.

Coquina

It is limestone or limestone that has a cemented rough texture. This type of limestone is composed of the remains of the shell of an organism that undergoes a process of sedimentation. This rock formation process usually occurs in coastal areas where there is a separation of shell fragments of the same size by waves or ocean waves.

Fossiliferous Limestone

Is limestone which has a lot of fossil content in it. This is because the fossiliferous limestone is formed due to the dominance of an organism's skeleton and shell.

Lithographic Limestone

It is a type of limestone with a very dense shape and consists of fine grains. Uniquely, the fine grains that make up the limestone have a very uniform size. This is what makes this rock very smooth when touched.

Oolitic Limestone

It is a limestone whose main composition is dominated by calcium carbonate "oolites". The shape is in the form of small circles resulting from the concentric precipitation of calcium carbonate on the shell of fragments of organisms or grains of sand.

Travertine

Limestone is formed from the evaporation precipitation process. This type of rock often forms inside the cave. Examples are stalactite, stalagmite and flowstone.

That's some type of limestone that you should know. Hopefully the reviews about limestone or limestone above are useful.

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