Granite is one of the most durable
stones, which has been incorporated well in infrastructures of the present
times. The word "Granite" originates from the Latin word 'granum',
referring to the coarse-grained structure of this crystalline rock. It is
composed of quartz, feldspars and micas, as well as traces of a variety of
other minerals, which contribute to the color and texture of natural granite
stone. These granite stones are available in pink, dark gray or even black,
depending on their chemistry and mineralogy. A broad range of elegant
patterns and colors makes granite the most versatile of all stones. The
crystal size of the natural granite stone is somewhat determined by the rate
at which the granite cools: the slower the cooling process, the larger the
crystals grow. Occasionally some individual crystals (phenocrysts) are
larger than the ground mass in which the texture is known as porphyritic.
Indian Granite Stone is a common and widely occurring type of intrusive,
felsic, igneous rock with great strength and value. The density of granite
is 2.75g/cm3 (avg) and its viscosity at standard temperature & pressure
is ~4.5 • 1019 Pa·s. Natural Granite stone is typically the
hardest of the dimensional stones and can withstand the vagaries of nature,
effectively. The natural properties of this stone makes it the real "maintenance-free"
stone.
Occurrence
It is widely spread throughout the continental crust of the Earth and is
generously found as a basement rock that underlies in the relatively thin
sedimentary veneer. This light colored stone often occurs as relatively
small, less as 100 sq. km stock masses (stocks). In batholiths they are
often associated with organic mountain ranges. In some areas very
coarse-grained pegmatite masses are found with granite. Outcrops of granite
usually form into tors, and rounded massifs. Granites also occur in circular
depressions that are surrounded by a range of hills and are formed by the
metamorphic aureole or hornfels.
Origin
This versatile rock has been intruded into the crust of our planet during
all geologic periods, though much of it is of Precambrian age. Granite is an
igneous rock which is formed from magma and is currently found only on Earth
where it forms a major part of continental crust. Granitic magma has many
potential origins but it must intrude other rocks. Most granite intrusions
are located deep within the crust, which is usually more than 1.5 kilometers
and up to 50 km depth within thick continental crust. Small embankments of
granitic composition known as aplites are often affiliated with the margins
of granitic intrusions. The origin of granite is contentious and has led to
varied schemes of classification. Classification schemes are regional and
include French, British, and American systems.
Geochemical Origins
Granite is a ubiquitous component of the crust that has crystallized from
magma and has compositions at or near a eutectic point. Magmas evolve to the
eutectic owing to the igneous differentiation, or because it represents low
degrees of partial melting. Fractional or partial crystallization serves to
reduce a melt in iron, titanium, magnesium, sodium and calcium. They also
enrich the melt in silicon and potassium, which is and alkali feldspar (rich
in potassium) and quartz (SiO2), are the two of the defining constituents of
granite.
This process functions is indifferent to the origin of the parental magma
and its chemistry. However, the composition of the magma which is different
in the final product- granite leaves certain geochemical and mineral
evidence as granite's parental rock. The absolute mineralogy, texture and
chemical composition of the granite is often unique as its origin. For
example, a granite that has been formed from melted sediments may have a
larger portion of alkali feldspar, whereas a granite, which has been derived
from melted basalt may be richer in plagioclase feldspar.
