Location: Ondo, Ogun, Ekiti, Kaduna, Kogi and Kwara.
ORIGIN AND OCCURANCE
Feldspars occur in all classes of rocks. They are widely distributed in igneous rocks, which indicates that they have formed by crystallization from magma. Physical weathering of feldspar-bearing rocks may result in sediments and sedimentary rocks that contain feldspars; however, this is a rare occurrence because in most environments the feldspars tend to be altered to other substances, such as clay minerals. They also may be found in many metamorphic rocks formed from precursor rocks that contained feldspars and/or the chemical elements required for their formation. In addition, feldspars occur in veins and pegmatite, in which they were apparently deposited by fluids, and within sediments and soils, in which they were probably deposited by groundwater solutions.
Feldspar are a class of rock-forming tectosilicate minerals that contains calcium, potassium or sodium and makes up more than half of the earth’s core by weight. Its minerals are largely found in igneous, sedimentary and metamorphic rocks spread across different parts of the world. These minerals are such essential components of these rocks that the classification of a number of rocks is based on the feldspar mineral content.
To appreciate the importance of feldspar as a rock-forming mineral, let’s consider its abundance in Earth’s crust. Most of Earth’s continental crust is made up of igneous rocks such as granite, diorite, and granodiorite. Feldspars are also important constituents of gabbro and basalt, which are the primary types of rock in Earth’s oceanic crust. The accompanying chart shows how these rocks are made up mostly of feldspar minerals.
Feldspars are a group of rock-forming aluminium tectosilicate minerals, containing sodium, calcium, potassium, or barium. The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium-sodium) feldspars. Feldspars make up about 60% of the Earth’s crust, and 41% of the Earth’s continental crust by weight.
The most important properties of feldspar to downstream industries and many other industries are their alumina and alkali content. For this reason, alkali feldspars (potassium feldspars) have a wide range of applications in paint industries, glass, and ceramic making industries. Here are some of the applications of potassium feldspars.
Glass: Feldspar is a critical material in the production of glass. It is also a crucial raw material in its production as it tends to act as a fluxing catalyst. As a fluxing catalyst, it reduces the temperature of quartz while simultaneously helping to keep the viscosity of the produced glass at the right correct range. It is the alkali content of the feldspar that helps it function effectively as a flux in glass making.
Fillers: Feldspars are functionally used as extenders and fillers in paints, rubbers, and plastics. It is an effective filler because of a number of factors. These factors include its stable pH, high chemical inertness, good dispersibility, impressive refractive index, resistance to frosting, high resistance to abrasion and low viscosity at high filler loading. In general, the products used for such purposes are fine-milled grades.
Ceramics: Putting things in perspective, feldspar is considered the other most critical ingredient – besides clay – in the production of ceramics. It doesn’t have a definite melting temperature, as it melts slowly throughout various temperatures. This is one of its advantages as it accelerates the melting of clays and quartz, while simultaneously allowing modulation of this crucial stage in the production process. They are generally used as fluxing catalysts to produce a glassy coating at low temperatures. They are also used as a source of alumina and alkalis in glazes.
Porcelian: Feldspar, along with kaolin and quartz (as a form of silica) are the primary components in modern porcelain ceramics. These are ‘hard paste porcelain’ types, which compared to ‘soft paste’ are fired at temperatures around 1,400 °C, whereas ‘soft’ types are fired only at 1,200 °C. These types of porcelain are regarded as stronger and much less likely to crack than ‘soft paste’ variants. Depending on firing type, it can resemble conventional stoneware or earthenware. As with all ceramics, it is now understood that one of the major reasons for feldspar’s inclusion is for its superior fluxing capabilities.
Enamel glazes: In enamel glazes, feldspar helps to enhance the aesthetics of the final product by ensuring that there are no errors in the final product. It is useful in the manufacturing of sanitary ware, ceramic tile glazes, tableware, giftware, electrical, and enamel frits. In sanitary wares, feldspars are used to facilitate the optimization process.