Your sedimentary rock is probably a sandstone. Sandstone
are made up of sand grains which are actually tiny pieces of quartz. Sandstones
can be formed in a range of different environments: under water where layers of
sand build up or in deserts. Sandstones formed in deserts are usually red
in colour as a result of the grains becoming oxidised, and the grains are
usually quite frosted. This frosting is caused by the grains blowing around in
the wind and banging together which dulls the surface.
Sandstones from the lower Triassic period (approx. 220 million years ago) can be found
at Park Hall National Nature Reserve in Stoke-on-Trent.
