Page 18 - Curriculum Visions Dynamic Book

Building stone
The most common form of building stone that uses calcium-rich material is made of calcium carbonate, usually in the form of limestone. Many limestones are easy to cut up into blocks and so make good building stones. Calcium carbonate is also found as marble.
Limestone
Limestone is used the world over by architects to make buildings. It is reasonably hard, quite attractive, and yet can be easily sculpted and cut in any direction. Limestone comes from quarries where thick bands of rock are found.
Sometimes limestones are chosen for the fossils they contain. When cut and polished, the fossils make interesting decorations.
Limestone will react with rainwater and weather over a period of time. This can readily be seen in many old buildings.
Marble
Marble is limestone that has been naturally altered by millions of years in the depths of ancient mountains. The impurities show up
as the mottling and streaks: red for iron, blue for graphite (a form of carbon) and so on.
The streaks were formed when the marble became so hot that the impurities began to melt and run through the limestone.
Marble is much harder than limestone and more difficult to work with. It is used as the facing for many buildings and for some of the world’s finest sculptures. Buildings containing huge amounts of marble include the White House in Washington DC and the Taj Mahal in India.
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 The Capitol Building, Washington, DC, uses marble siding to provide a striking appearance.
 The Taj Mahal, India, the world’s most famous marble-clad building.
 A piece of marble.