Sandstone is a type of rock composed mainly of sand that has been bonded together by pressure or by minerals. The sand commonly consists of grains of quartz, feldspar, and other minerals. It may also include organic matter or rock fragments. The minerals that cement the grains include quartz, pyrite, or calcite. The color of sandstone ranges from cream or gray to red, brown, or green, depending on the cements and impurities in the sand. The composition of sandstone is quite similar to that of sand, that essentially consists of quartz. The natural cementing material which binds the sand together as rock is usually composed of silica, calcium carbonate, or iron oxide. The percentage constitution of each constituent varies between certain limit, which is as follows:

SiO2 ---------------------------------- 93-94%
Alumina(Al2O3) ------------------- 1.4 to 1.5%
Iron(Fe2O3) ------------------------ 1.5%-1.6%
Lime(CaO) -------------------------- 0.8% to 0.9%
Soda(Na2O) & Potash (Kro) -- 1.0% to 1.2%
Loss On Ignition(LOI) ----------- 1.0% to 1.2%
Magnesia(MgO) --------------------0.2 to 0.25%

They are highly resistant to acids, alkalies and thermal impact and their insolubility in acids and alkalies is about 97%