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-HISTORY OF GRANITE-

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What is granite?

Granite, from the Italian granito (meaning grained), is a type of volcanic rock containing crystallized minerals such as feldspar, quartz and mica. Formed deep within the earth's crust, the colors and patterns of granite are determined by the minerals, their varying concentrations, temperature, pressure and the rate at which the rocks cool down on their ascent to the earth's surface. It is this range of colors and patterns that make granite such an appealing and unique material to use for kitchen worktops, tiles and flooring within the home.

Coarse-grained igneous rock of even texture and light color, composed chiefly of quartz and feldspars. It usually contains small quantities of mica or hornblende, and minor accessory minerals may be present.

Depending on the feldspar present, granite may be pink, dark gray, or light gray. It is commonly believed to have solidified from molten rock (called magma) under pressure. However, some granites show no contacts with surrounding wall rock, but instead gradually grade into metamorphic rock. Others show relic features found in sediments. This evidence suggests that some granites are not igneous in origin, but metamorphic.

Some granites are the oldest known rocks on earth; others were formed during younger geologic periods. Crystallized at depth, granite masses are exposed at the earth's surface by crustal movement or by the erosion of overlying rocks.

Very coarse-grained granite, called pegmatite, may contain minerals and gemstones of economic value. Such pegmatites are found in the Black Hills of South Dakota. Granite has been used since ancient times as a building material.