is the most abundant silicate with Potassium, sodium, and
calcium or mixtures of these elements. The common feldspar
is potassium feldspar, namely orthoclase K2O, Al2O36
SiO2, sodium feldspar is albite Na2O, Al2O36
SiO2, and calcium feldspar is anorthite CaO, Al2O36
SiO2, They occur in various colors but the pink
brown and grey ones are common.
is mainly utilized in the manufacture of glass, pottery,
ceramics, vitrified enamels, special electrical porcelain,
wind plates and opalescent glass as well as glass ware In
the ceramic industry feldspar is used both in the body and
an a glaze for china wares, It is also used an a binding
agent in the manufacture of abrasives.
is no BIS specification for feldspar specifications of feldspar
in various industries as prescribed by them is as below:
in used in the form of powder as also lumps which have SiO2
- 60% min., Al2O3 18% min.,
and K2O / Na2O - 10% minimum. While
CaO, Fe2>O3should be low 0.6% and
0.45% respectively, LOI should not be more than 2%.
is mainly used as a fluxing agent and white wares contain
good proportion of feldspar. There are two grades is used,
Grade - I should have SiO2 - 68% maximum, Fe2O3
should be below 0.1% while ratio of K/Na should be 2:1.
In Grade - II SiO2 is 72% maximum and Fe2O3
is same as that of Grade-I i.e. 0.1% max CaO should be in
traces while MgO should not be present.
glass industry potash feldspar is preferred as it introduces
potash for clarity and alumina for durability and also controlling
viscosity of molten glass. It should contain 10 to 13% of
Na2O and K2O combined, 15 to 18% of
Al2O3, 65 to 68% of SiO2
and Fe2O3 below 0.3%, while the size
should be 30 to 80mesh.
already mentioned earlier feldspar in added as one of the
batch constituent for refractory. Here also 11 to 12% of
combined Na2O and K2O are preferred
while SiO2 should be within 60 and 65%, A12O3
should be 18 to 19%, Fe2O3 should
be below 1.5%, PCE = 4 orton cone
and LOI should be
below 0.8%. Size preferred is 2.5 – 10 cm.
finds use in electrode manufacture it acts as a flux and
forms slag, which protects molten metal from oxidation.
For this, Potash feldspar having 13 to 14% of K2O,
1 to 3% of Na2O, 63 to 65% SiO2, 17
to 20% of Al 2O3 and Fe2O3
up to 0.3% is preferred. LOI should be maximum up to 1%.
Size 0.2 to 0.06.
the inventory of feldspar as on 01.01.1985 some data on
actual uses in industries like glass, ceramic, pottery and
abrasive has been reported by lessees from there lease holds
and accordingly the reserves in these areas have been classified.
For rest of the reserves in other areas where there is no
information available the reserves have been classified
specification for ceramic and glass grades are given as
(Potash feldspar): SiO2
below 0.3% (max.) 15%