these
are Rubellite (pink Tourmaline) and red Quartz (" Bohemian Ruby ").
Here again the inferior hardness will distinguish them from the Baby in
cases where one can scratch the specimen, and also the lower specific
gravity as compared with Ruby. Yellow Topaz which has been turned red
by heat (" Brazilian Ruby ") is distinguished by the same two tests.
Red Fluor Spar, which is only very rarely used as an imitation Ruby, is
again softer and less dense. The colour of the Ruby is perhaps most
nearly imitated in glass, but glass is singly refracting and relatively
very soft. Quartz which has been stained in cracks can be recognised by
these cracks, which can never be quite hidden ; it is called Rubasse.
Sapphire.—What
has been said of the origin and mode of occurrence of Ruby applies very
much to Sapphire too, the one rarely being found without the other,
though at some localities one is more abundant than the other.
The
most important Sapphire mines are in Siam, at Battambang, but Sapphires
are also found with the Rubies in the mines of Chantabun and Krat. At
Battambang they occur in a sandy deposit; this is washed and picked in
the usual manner. It is noteworthy that the larger stones are usually
of better quality than the smaller. Gems of very fine cornflower blue
colour are obtained from Siam; they are strongly dichroic and show
images respectively blue and green.
In
the Burma Ruby mines they are also found, but in much fewer numbers
than are the Rubies, though the Sapphires often exceed the Rubies in
size. They are of good quality, faultless stones of 80 carats having
been
