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Marble
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- Marble,
formed from limestone with heat and pressure over years in the
earth's crust. These pressure or forces cause the limestone to
change in texture and makeup. The process is called
recrystallization. Fossilized materials in the limestone, along
with its original carbonate minerals, recrystallize and form
large, coarse grains of calcite.
Impurities present in the limestone during the recrystallization
period affect the mineral composition of the marble which is
formed. At relatively low temperatures, silica impurities in the
carbonate minerals form masses of chert or crystals of quartz.
At higher temperatures, the silica reacts with the carbonates to
produce diopside and forsterite. At a very high temperatures,
rarer calcium minerals, such as larnite, monticellite, and
rankinite, forms in the marble. If water is present, serpentine,
talc, and certain other hydrous minerals may be produced. The
presence of iron, alumina, and silica may result in the
formation of hematite and magnetite.
The minerals that result from impurities give marble a wide
variety of colors. The purest calcite marble is white in colour.
Marble containing hematite are reddish in color. Marble that has
limonite is yellow, and marble with serpentine is green in
colour.
Marble does not split easily into sheets of equal size and must
be mined with care. The rock may shatter if explosives are used.
Blocks of marble are mined with channeling machines, which cut
grooves and holes in the rock. Miners outline a block of marble
with rows of grooves and holes. They then drive wedges into the
openings and separate the block from the surrounding rock. The
blocks are cut with saws to the desired shape and size.
- Marble Slabs: Marble slabs are fabricated by
the sawing of marble blocks in the desired thickness. They are
used for wall cladding and as building stones they occupy a
unique position. Owing to their pleasing colors, aesthetic
appeal, excellent polish and durability, marble slabs are widely
used as counter tops, table tops, kitchen tops and
vanities.
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