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Natural stone is a general term employed to cover all types of rock of
whatever origin found in the earth's crust. Industrial or, in commercial
terms, natural stone is used for rock which is produced with legal permission,
processed and/or unprocessed, shaped or unshaped.
For example, just as stones obtained from a limestone quarry can be used
as raw material in the production of cement or lime by means of certain
processes, they can also be used as foundation stones simply by
chipping and shaping, as cement aggregate by being fragmented and
sifted and as facing stone by being cut from measured blocks and polished.
As can be seen from this example, the term "Natural Stone" is
in the nature of an "Umbrella Concept" covering a number of different
functions in accordance with use and aim.
In buildings, dressed and polished stone is usually employed. Recent
times have seen the use on facades of unpolished stones with a rough
surface. Stones with deliberately produced rough surfaces are used in
vertical surfaces (interior or exterior), in floor covering, on the steps of
stairways and for decorative purposes. Stone responds quite naturally
to polishing, and its use is in no way inconsistent with the commercial
definition of marble, which will be explained below.
The term "Building Stone" refers to stone used in the construction of
roadways and pavements, while the term "border stone" refers to stone
used as material in walls and retaining structures, roofs, shore defenses
and dams, and for the production of aggregate.
In the cutting of stone for these purposes use is made of natural discontinuities and
explosives are employed in quarry production. The product displays differences
in size and characteristics. In block quarries, small blocks are
generally used as building material. In certain circumstances, building
stone divided up by natural discontinuities into sheets is used as facing
stone. This group includes metamorphic stone such as gneiss, phyllite,
graphite and schist.
In recent years, "Building Stone" has also been included in the definitions
given above, such as cement, ceramics and glass under the title
"Stone-Clay Industry". In other words, building stone is also accepted
as an industrial raw material in the modern sense.
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