You must have heard the sound of conch (shankh) blowing in the temples. You must have also seen big and small conches at sea-shores and on the river banks. Some conches are so small that they can be seen only with the help of a magnifying lens, whereas there are others as big as measuring up to 120 cm.
Do you know what these conches are and how they are formed? They are the body shells of aquatic creatures. These creatures are called mollusks. Some 60,000 species of the mollusks have so far been studied by the scientists. As the size of the mollusk increases, the outer shell also increases and becomes harder. They are made up of calcium carbonate (lime). The mollusk collects lime from the sea water and deposits it in its outer shell. When the mollusk dies, the shell floats and comes to the surface of water.
The shell of the mollusk has three main layers. The outer layer of the shell is made up of smooth material like the oyster and contains absolutely no lime. The layer below this i.e. the second layer is made up of calcium carbonate. The lowest layer that is the third layer is a group of many thin layers, which are made up of oyster-like material and calcium carbonate. The conches are of many colours. They have many stains and stripes. These stains, colours and stripes have their origin in some colourful materials present in the glands of the mollusk. These colours, stripes and stains enhance the beauty of the conches.
The conches not only protect the mollusk, but they are also very useful for us. In ancient times people used mollusk shells as coins. Small conches are even used as part of necklaces. They are used as decoration pieces in homes. Buttons are made from small shells. Aquatic animals with shells have been existing for billions of years. After their death these shells deposit themselves on the sea-bed which forms rocks of limestone.