and
breaks unevenly. The lustre of turquoise is waxy and the colour is
sky-blue, bluish-green, apple-green, and greenish-gray. The colour is
liable to change, however, the blue becoming a pale green. Artificial
means are resorted to for " improving " stones of a poor colour, but a
washing in strong ammonia water will expose the fraud. This solution
will not affect the colour of the true turquoise, but as soap and water
does, possessors of rings set with turÂquoise should never wash their
hands without removing their rings.
The chemical composition of the turquoise is
a hydrous phosphate of aluminium and copper,
and the principal components in a hundred
parts are: phosphoric acid, 30.9; alumina,
44.50; oxide of copper, 3.75; water, 19.
The exposure of turquoise to a sufficiently high degree of heat will extract the water and cause it to crackle.
The
turquoise most highly prized comes from Persia, and the most celebrated
are those from an old mine, the Abdurrezzagi in a district of the
Nishapur province in the north-eastern part of the country. Less valued
specimens come from Asia Minor, Turkestan, and the Kirghiz Steppes. The
Egyptians mined tur-
