What is silica? What are silica applications?

What is silica? What are silica applications?
Generally, the usages of silica included: glass industry, porcelain industry, production of ferrosilicon, ceramic industry, production of limy sand brick, casting, silicate sodium production, production of other silicon materials, as a semiconductor in electronic industry and production of glass wool.
Noticeable amount of crushed sandstone used as building materials.
Used silica in every one of these industries should have specific quality, chemical compound, mineralogy structure and physical properties of silicone determine quality and its usages in anyone of said industries. Chemical compound of silicone included percentage of SiO2 in stone and percentage of other oxides used with SiO2 in different deposits and if percentage of every one is more than certain limit, its usage in different industries is being limited and impossible.
In addition to percentage of SiO2, stone mineralogy structure has role in determination of quality and its usages because SiO2 may be as types of silicates, thus, this issue will have effects on determination of mineral processing and process of impurities elimination.
Physical properties of silica have also effect on crushing and grading of produced silica powder and determination of usage items of produced powder.