Best for Ceramic & Sanitary Ware Manufacturing - Application in both Glaze (K2O > 11.5%) & Body (K2O >10.5%) - gives White Firing Colour
Glass Grades - better fluxing from K2O > 10% (total alkalies > 13%), Alumina > 17% for strength, Low Iron Fe2O3 at < 0.5%
High Potash K2O >11% for Flux coated Welding Electrodes
Feldspar is the most common rock-forming mineral (about 60% of the earth's crust) (Kauffman and Van Dyk, 1994). The mineral name feldspar is derived from the German words feld + spar. The word "feld" is "field" in German and "spar" is a term for light colored minerals that break with a smooth surface. Feldspar minerals are usually white or very light in color, have a hardness of 6 on the Mohs’ Scale of Hardness and perfect to good cleavage (plane of breakage) in two directions.
Feldspar is a common name that applies to a group of minerals with a general chemical formula of x Al(Al,Si)3O8, where x can be sodium (Na) and/or calcium (Ca) and/or potassium (K). (Specific compositional varieties (i.e. albite, microcline…) are discussed under Mineral Descriptions).
Feldspar occurs in igneous, metamorphic and sedimentary rocks and thus can be found throughout North Carolina. It is more commonly found in igneous and metamorphic rocks of the Blue Ridge and Piedmont provinces. Feldspar weathers to kaolin which is the main clay mineral used in ceramics and fine pottery.
In the manufacture of high-class, colourless glass, feldspar should have a maximum of 0.1% Fe2O3 though upto 0.3% is permissible.
The History Says The word comes from the German "feldt spat", meaning "field spar", "spar" meaning common clevable material - the material dredged up on farm lands during plowing. Most of them are not affected by acid (exception the Ca rich plagioclase - Anorthite). Orthoclase got is name from the Greek phrase meaning "straight fracture", Microcline from a Greek phrase meaning "small incline", and Plagioclase from the Greek phrase meaning "oblique fracture".
The Present Scenario Feldspar is used as bonding agent along with magnesium oxide, magnesium chloride and other synthetic glue in the manufacture of abrasives, wheels, discs and other shapes.
FELDSPAR comprises a group of minerals containing potassium, sodium, calcium and aluminium silicates. They are the most common rock-forming minerals. The common feldspar is potassium feldspar, namely, orthoclase (K2O, Al2O3, 6SiO2). Sodium feldspar is albite (Na2O, Al2O3, 6SiO2) and calcium feldspar is anorthite (CaO, Al2O3, 2SiO2). A variety of crossed, hatched, twinned orthoclase (to be seen under the petrological microscope only) is called microcline. Sodium and calcium feldspars form an somorphous mixture known as plagioclase feldspars.
In between sodium and calcium, the other feldspars of the plagioclase series are oligoclase, andesine, labradorite and bytownite. They are composed of suitable proportions of sodium and calcium with an increasing percentage of calcium begining from mineral oligoclase to bytownite, turning completely into calcium feldspar (anorthite). A rock containing only plagioclase feldspars is called anorthosite.
The commercial feldspar is orthoclase. The potassium molecule is replaced by sodium to some extent and hence, orthoclase feldspar usually contains a small percentage of sodium. The composition range of the commercial feldspar varies within the limits of potash, soda and upto oligoclase.
Potash and soda feldspar occur as essential constituents of granite, syenite and gneisses. However, workable deposits are found in pegmatite veins consisting mainly of feldspar, quartz-feldspar veins and also occur with mica pegmatites. Feldspar is of widespread occurrence and is mined in almost all countries.
Feldspar is generally used for three purposes
In making the body composition of several types of procelain, china and earthenware and also in the preparation of glazes and enamel.
As an important ingredient in the glass sand batch.
As a bonding agent in the manufacture of bonded abrasives like wheels and discs of garnet, corundum, emery etc.