Testing the presence of metals in soil

1200. The presence of metallic oxides in a soil may generally be known by their colour. Ferruginous soils are red or yellow; cupreous soils, interspersed with greenish streaks, &c. Cupreous impregnations of soils are rare; and the usual green matter in such soils as the green sand of English geologists, appears to be coloured by iron, which is almost the only metallic impregnation in considerable quantity in any soil.