\Sand"stone`\, n.
A rock made of sand more or less firmly united. Common or
siliceous sandstone consists mainly of quartz sand.
Note: Different names are applied to the various kinds of
      sandstone according to their composition; as, granitic,
      argillaceous, micaceous, etc.
{Flexible sandstone} (Min.), the finer-grained variety of
   itacolumite, which on account of the scales of mica in the
   lamination is quite flexible.
{Red sandstone}, a name given to two extensive series of
   British rocks in which red sandstones predominate, one
   below, and the other above, the coal measures. These were
   formerly known as the Old and the New Red Sandstone
   respectively, and the former name is still retained for
   the group preceding the Coal and referred to the Devonian
   age, but the term New Red Sandstone is now little used,
   some of the strata being regarded as Permian and the
   remained as Triassic. See the Chart of {Geology}.