Limestone—Commonplace but Precious
By Awake! correspondent in Belgium
PRECIOUS STONES! The term conjures up visions of a multicolored blaze: diamonds, emeralds, rubies, sapphires, limestone. Limestone? Yes, lowly limestone is a precious stone of sorts.
In Belgium, as in most places, you find limestone almost everywhere. It is used in the construction of simple homes as well as stunning monuments. At the same time, you find it underfoot as gravel. Just what is this material that is found in so many places?
Limestone is a calcareous rock that contains more than 50 percent calcium carbonate. It formed long ago as a result of various processes, which produced different kinds of limestone. Marine animals such as clams, snails, and corals draw calcium carbonate from the water and use it to make their shells and bones. The skeletal remains are left behind when the animals die. Thus, The World Book Encyclopedia observes: “Most of the limestone layers in all parts of the earth were once shell or coral sand and mud.”
Limestone is also formed when calcium carbonate is forced out of solution by evaporation of the water in which it is dissolved. Some precipitated directly from water, accumulating around certain springs as well as in lakes and oceans. Upheavals in the earth’s crust have caused portions of land formerly underwater to rise above the surface of the water. (Compare Psalm 104:8.) Limestone is thus plentiful. According to one estimate, it makes up 20 percent of all sedimentary rocks. But limestone is also eminently useful.
Chalk, which is composed of microscopic skeletons of tiny marine life, is limestone. But so is marble. Marble is formed when limestone deposits are subjected to heat and pressure over long periods of time. Many famous caverns, such as Carlsbad Caverns in the United States, have beautiful limestone stalactites and stalagmites. These are formed by the dripping of water that contains calcium carbonate.
The Challenge of Getting It
Limestone, however, is not easily obtained. Open excavations, or quarries, are created by removing the earth that covers the limestone deposit. Laboriously, and with incredible perseverance, quarry workers of earlier times dug narrow trenches in order to lift up strips of stone, setting aside the largest blocks. Then came the difficult job of breaking up these blocks with sledgehammers.
Nowadays, machines accomplish these grueling tasks. Even though work in a quarry is dangerous, the need for the stone is so great that man has had to learn to deal with the risks of mining it. Good-quality limestone is often extracted by use of low-energy explosives. Better still, it may be cut out with saws.
Building With Limestone
Limestone is ideal for some construction purposes. For one thing, it provides good insulation for a building. A 12-inch-thick [30 cm] limestone wall keeps the temperature of the interior steady even when the outside temperature varies as much as 35 degrees Fahrenheit [20° C.]. The mass of the stone wall causes its inside face to remain at average room temperature.
Limestone is also good for soundproofing. In addition, when limestone is correctly handled, it can even make itself waterproof. The carbon dioxide in rainwater reacts with the stone and progressively forms a waterproof protective layer on the surface.
Furthermore, limestone is beautiful. The famous Arc de Triomphe in Paris is but one example of a famous limestone structure. Also noteworthy are the great pyramids of Egypt, constructed of limestone blocks weighing as much as 16 tons! Marble is a form of limestone that can be polished. Its enduring luster and beauty made marble the choice of such sculptors as Michelangelo.
Limestone and Lime
Of course, not all limestone is put to such an outstanding use. Much of it is fed into crushing mills, the first step in processing it into a variety of important products. Since Bible times, for example, man has known how to produce lime (calcium oxide) by the calcination of limestone. Back then, this was done by burning it in conical or cylindrical limekilns. Lime served as the key ingredient in mortar and was used in ancient times in plastering walls and in whitewashing walls and graves.—Deuteronomy 27:4; Ezekiel 13:10; Matthew 23:27; Acts 23:3.
Lime still has many important uses. In some countries the water is drinkable because lime is used to purify it. Limewater, which contains calcium carbonate or calcium sulfate in solution, is a protection against diarrhea. Lime is also used to neutralize the acidity of soil. It increases the water and air permeability of soil, thus helping in the production of nutritious foods. And lime is even used in the manufacture of sugar.
Really, the list of uses of limestone and its products is extensive. Admittedly, though, obtaining limestone creates problems. Opencut quarries are often abandoned and become real eyesores. Villages around the quarries may be covered with the characteristic white dust, and people nearby are annoyed by the noise and vibrations of blasting.
Nevertheless, when you consider all its uses, limestone is really quite a precious stone. True, it is not a diamond. But then, what building or monument was ever constructed with diamonds?