Vivianite contains ferric oxide, phosphoric acid and water, but in variable proportions. The original composition, expressed by Fe{2}(PO{4}){2} + 8H{2}O{2}, corresponds to 43·03% of ferrous oxide, 28·29% of P{2}O{5} and 28·68% of water; but, in the air, part of the ferrous phosphate is oxidised to basic ferric phosphate, so that the content of ferrous oxide may range from 9·75 to 42·71%, and that of ferric oxide between 1·12 and 38·20%. Vivianite is also sold as blue ochre, and is now seldom used as a painters’ colour, owing to the introduction of a large number of artificially prepared blues, which are superior to vivianite in colour and are cheaply made. However, it can still find application in localities where it is obtainable in quantity. (E) GREEN EARTH PIGMENTS The green earth pigments comprise green earth (Verona green) and malachite. Like the blue earths, they cannot lay any particular claim to beauty, but they are very cheap, and consequently are largely used where low price is the chief consideration. _Green Earth_ In Nature, green occurs as an entirely non-crystalline earthy mass, which is probably a decomposition product of augite. It has a close, earthy fracture, a colour between seladon and olive green, and a slightly greasy appearance. In point of chemical composition it consists of silica, alumina, magnesia, sodium, potassium, ferrous oxide and water, the usual representative formula being ROS{1}O{2} H{2}O, in which RO symbolises a metallic oxide. The colour is due to ferrous oxide; and if left exposed to the air for a long time, or subjected to powerful calcination, the great affinity of ferrous oxide for oxygen causes the colour to turn red and red-brown. Green earth is found in many localities, _e. g._ Bohemia, Hungary, the Tyrol and Cyprus, the finest, however, occurring near Verona, on which account it is known as Veronese earth. _Malachite_ The commercial pigment consists of powdered malachite, a mineral which usually occurs in compact masses of a handsome emerald green colour, though isolated lumps exhibit considerable variation in shade, some of them being dark green and others very pale. In chemical composition, malachite is closely allied to azurite, consisting of cupric oxide, carbon dioxide and water, and the difference is entirely one of percentage proportions. The formula is CuCo{3}, Cu(OH){2}, or Cu{2}(OH){2}CO{3}, corresponding to 71·90% of cupric oxide, 19·94% of carbon dioxide and 8·16% of water.