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Granite
GRANITE:
Granite, igneous rock of visible crystalline formation and
texture. Lt is composed of feldspar (usually potash feldspar and
oligoclase ) and quartz , with a small amount of mica (biotte or
muscovite ) and minor accessory minerals , such as zircon, apatite ,
magnetite , limenite , and sphene. Granite is usually whitish or gray
with a speckled. Appearance caused by the darker crystals. Potash
feldspar in parts a red or flesh color to the rock. Granite
crystallizes from magma that cools slowly, deep below the earth’s
surface. Exceptionally slow rates of cooling give rise to a very coarse
grained variety called pegmatite. Granite masses, and it is the most
common intrusive rock exposed at the earth’s surface.
Although granite has been known as igneous rocks derived from,
molten masses or magmas, but there is wide evidence that the origin of
some granite may be attributed to regional metamorphism or preexisting
rocks, rearrangement and recrystallization taking place without a
liquid or molten stage.
The specific gravity of granite of granite ranges from 2.63 to
2.75. its crushing strength is from 1050 to 14,000 kg per sq cm (
15,000 to 20,000 lb per sq in ) Granite has greater strength than
sandstone , limestone , and marble and is correspondingly more
difficult to quarry. Lt is an important building stone,
The best grades being extremely resistant to weathering.
Normally granite is classified in three different groups:
● FINE GRAIN: Fine grain granites are those which the feldspar
crystals average about 1/16 – 1.8 ˝ in diameter.
● MEDIUM GRAIN: Medium grain granites are those in which the
feldspar crystals average about 1.4″ in diameter.
● COARSE GRAIN: Coarse grain granites are those in which feldspar
crystals average 1/2″, and greater diameter or several centimeters in
maximum dimension. Coarse grain granites may have a lower
density.
In recent years about 83 percent of the stone used for monuments has
been granite, about 17 percent, marble.