is called _mina nova_.[4]

[4] The pink topaz is made from the yellow, which, when of
intense colour, is put into the bowl of a tobacco pipe, or small
crucible, covered with ashes or sand: on the application of a
low degree of heat, it changes its colour from a yellow to a
beautiful pink. It contains fluoric acid, which may be the means
of this change.--_Mawe_.

_Why is ruby of such a brilliant colour?_

Because a sixth of it is chromic acid, while other gems, as the garnet,
are coloured by oxide of iron. The most esteemed, and at the same time,
rarest colour, of the oriental ruby, is pure carmine, or blood-red of
considerable intensity, forming, when well polished, a blaze of the most
exquisite and unrivalled tint. It is, however, more or less pale, and
mixed with blue in various proportions; hence it occurs rose-red and
reddish white, crimson, peach-blossom red, and lilac blue--the latter
variety being named oriental amethyst. A ruby perfect both in colour and
transparency, is much less common than a good diamond, and when of the
weight of three or four carats, is even more valuable than that gem. The
king of Pegu, and the monarchs of Siam and Ava, monopolize the rarest
rubies; the finest in the world is in the possession of the first of
these kings: its purity has passed into a proverb, and its worth when
compared with gold, is inestimable. The Subah of the Deccan, also, is in
possession of a prodigiously fine one, a full inch in diameter. The
princes of Europe cannot boast of any of a first rate magnitude. Mr.
Mawe, from whose interesting work we abridge these particulars,
considers the oriental sapphire to rank next in value to the ruby. Among
the British crown jewels is an inestimable sapphire; it is of the purest