Silica is the name given to a group of minerals composed of Silicon and Oxygen, the two most abundant elements in the earth’s crust. Silica found commonly in the crystalline state and rarely in an amorphous state. It is composed of one atom of silicon and two atoms of oxygen resulting in the chemical formula SiO2. The term crystalline refers to the fact that the silicon and oxygen atoms are arranged in a three dimensional repeating pattern. The main minerals included in this group are Quartz, Cristobalite and Tridymite. Quartz is the most common of them and after feldspar, is the second most abundant mineral on the earth’s surface. Crystalline silica, basically in the form of the Quartz, has been mined for thousands of years. Silica is hard, chemically inert and has high melting point because of the strength of the bonds between the atoms. These are prized qualities in various industrial uses. Quartz is usually colorless or white but is frequently colored by impurities such as iron. Quartz may be transparent to translucent, hence it is used in glass making, which has a vitreous luster. Depending on how the silica sand was formed, quartz grains may be sharp, angular or rounded.
High grade silica is normally found in unconsolidated deposits below thin layers of overburden. It is also found as “Veins” of quartz within other rocks and these viens can be many meters thick.
Silica Sand deposits are normally exploited by quarrying and the material extracted may undergo considerable processing before sale. The objectives of processing are to reduce impurities and increase the grade of Silica present and to produce the optimum size distribution of the product depending upon end use.