Elizabeth Wagner, age 13, of Tacoma, Wash., for her question:
WHERE DOES LIME AND LIMESTONE COME FROM?
Lime and limestone are raw materials that are found in every part of the world. Lime is a chemical compound that is made from limestone. Limestone itself was formed by the skeletons of billions of coral animals, limy plants and lime shelled mollusks that lived millions of years ago.
Both lime and limestone are used in great amounts in agriculture, building and as an industrial chemical.
The remains of coral animals and plants stacked up on the bottom of oceans around the world. Great beds of this material were squeezes and hardened until they turned into limestone.
Some limestone beds were not compressed as tightly as others. Those that were compressed very tightly became marble, from which the beautiful building stone is cut. Softer beds of limestone are called chalk or marl. Between these two are the beds of ordinary limestone. _
Some beds of limestone are many thousands of feet thick and stretch out over many miles. The beds vary in size at different depths in the earth.
Most limestone is obtained from the surface of the Earth since it costs less to remove it. But sometimes mines are dug because some types of underground limestone may have a certain purity or be of a special kind.
Limestone is chemically classified by the amount of calcium and magnesium carbonate it holds. High calcium limestone is usually hard and flinty. High magnesium limestone is softer and often Lull of tiny holes.
To make lime, raw limestone is heated in ovens called kilns for several hours at temperatures between 850 and 1,000 degrees Centigrade.
Hard limestone is used as a building stone. Crushed into bits, it is used for building roads and making concrete. Ground to dust, it is used as a soil builder to help grow better crops.
Lime is used to make mortar for plastering, for laying stone and brick and to make concrete more waterproof.
Limestone is also used in making iron and steel. Ground as a tine powder, it is used to make putty and to improve rubber tires and other rubber items.
Lime is also used in making leather goods, bleach, glass, iron, steel, paints, varnishes and plastics. Water is purified with lime and sewage is treated with it. The handy material is also used for whitewash, and after floods it is used to prevent diseases. Farmers often spray it on fruits and vegetables to repel insects.
Limestone is usually mined on a large scale and many machines are needed for the operation, such as conveyors, elevators, vibrating screens, washers, dryers and pulverizers. Because of this good equipment, many of the plants turn out 10 million tons of the product each year.
Limestone quarries in Indiana produce about two thirds of the building limestone in the United States. California and Wisconsin are other leading limestone pronucing states.