Feldspar 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 SiO_2, sodium feldspar is albite Na2O, Al₂O₃6 SiO_2, and calcium feldspar is anorthite CaO, Al₂O₃6 SiO_2, They occur in various colors but the pink brown and grey ones are common. 

Feldspar 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.

There is no BIS specification for feldspar specifications of feldspar in various industries as prescribed by them is as below:  

Abrasives: -

 Feldspar 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%.

 Ceramics: -

 It 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:

In 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.

Refractory:

 As 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.

Electrodes:

Feldspar 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.

 For 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 as "unclassified".

The specification for ceramic and glass grades are given as below:

i	Ceramic: SiO2 Fe2O3 K/Na	68% (min.) 0.1% (max.) 2:1
ii	Glass (Potash feldspar): SiO2 Fe2O3 K/Na	65% (min.) below 0.3% (max.) 15% (min.)