The mineral colours from tungsten are obtained by decompoing soluble tungstates by means of salts of the metals yielding insoluble phosphates. The tungstate of nickel produces a light green, tungstate of chromium a dark grey, tungstate of cobalt a violet or indigo blue, and tungstate of barium a bright white colour. Tungstic. acid alone gives a fine light greenish-yellow. All these colours may be employed for water- or oil-colour paints; the last is a really desirable and probably quite unchangeable colour.