and then the crystals are found in the debris in the beds of streams.
Red
corundum is supposed to be identical with the anthrax mentioned by
Theophrastus and to have been termed carbuncle during the Middle Ages.
The colour-tone of the ruby varies greatly, and the presence of deep,
intense tones of red causes the term " masculine" to be applied to a
gem, while the paler tints suggest the term " feminine." Rubies range
from a delicate pink tint through pale rose red to reddish-white, pure
red, carmine red, or blood red. A tinge of blue or violet is frequently
discernible in these shades. The desired tone in ruby colour was so
aptly compared by the Burmese to the blood of a freshly-killed pigeon
that the term " pigeon-blood" is the accepted qualification for the
colour of the choicest and costliest ruby gems. The colouring is not
always uniform, there sometimes occurring alternate layers of colours
and colourless stone; a process of heating usually renders the colour
uniform. The ruby does not lose its colour when heated, and hence it is
assumed that the colouring matter is not organic, as in that case it
would be destroyed, but is probably due to a trace of chromium. A
graduated increase
