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%




