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General
- Quartzite, not to be
confused with the mineral quartz, is a hard, metamorphic rock which was
originally sandstone.
- Orthoquartzite is a
very pure quartz sandstone composed of usually well rounded quartz
grains cemented by silica.
- Quartzite is very
resistant to chemical weathering and often forms ridges and resistant
hilltops.
- Pure quartzite is
usually white to grey.
- Quartzites often
occur in various shades of pink and red due to varying amounts of iron
oxide.
Process
- Sandstone is
converted into quartzite through heating and pressure usually related to
tectonic compression within orogenic belts.
- It is speculated that
the weathered zones may represent the lower parts of a previous deeply
weathered crustal layer which may be coupled to the formation of the
quartzitic inselbergs.
- Dissolutional
landforms on quartz sandstones or quartzites are also formed by a
variety of physical and chemical processes.
- The beds of limestone
alternate with layers of mostly sand or silt that was probably flushed
into the seas at river deltas. Layers of sandy materials were later
transformed by pressure (compaction) into sandstone or quartzite.
- Quartzite is a stone
composed almost entirely of quartz grains (or silica) which is derived
from sandstone or to a lesser extent chert. (Note: chert is a rock
composed mostly of the mineral chalcedony. Chalcedony is the name for
quartz with microscopically small crystals).
Application
- Quartzite -- usually
dyed to some pleasing color -- has been tumbled or otherwise fashioned
into decorative items such as the illustrated paperweight.
- A large percentage of
the quartzites used as gemrocks occur in metamorphosed sedimentary rock
sequences -- i.e., they are metamorphosed sandstones (metaquartzites).
- The texture anf
frictional properties of PCC overlays, one constructed with crushed
granite and the other with crushed quartzite coarse aggregate, were
compared to an overlay constructed with locally available crushed
limestone.
Market
- The export of blocks
and sawed slabs of quartzite and, above all, granites, reached the
figure of US $ 212 million and 1.2 million tons, which amounts to 20.32%
and almost 50% respectively, of the total exports.
- The greatest increase
in sales (+91.17%) was registered in the products of soapstone, while
the smallest change took place in solid quartzite (+1.6%).
- The South African
stand at the Marmomacc Dimension Stone Exhibition in Verona, received a
number of inquiries on the availability of good quality slate and
quartzite for the manufacture of tiles.
- The Indian and
Spanish exhibitors displayed an extensive range of slate and quartzite
tiles.
- It appears that there
is good export potential for slate and quartzite.
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