Sandstone that is rich in silica, particularly as free silica as opposed to silicates; the silica characterizes the cement or matrix which binds together the quartz particles of which sandstone is mainly composed. Pure siliceous sandstone is chemically inert, making it able to withstand a smokey environment; it is therefore a popular building stone in industrial areas. It is also hard and durable but difficult to work. Pure siliceous sandstone is white or cream in color; colors are due to impurities: yellow and red colors are due to the presence of iron oxides; green from glauconite; and black from manganese dioxide.
