32 SPINEL RUBY. 
was a ruby which measured two inches in length, and 
one inch in breadth. It was, however, interesting only 
as a specimen for a cabinet, for it had, in various direc- 
tions, a great number of small hair-like tubes running 
through it. 
The hardness of this stone is such that the ancients 
do not appear to have possessed the art of cutting it ; 
and, in the improvements which of late have been made 
by Mr. Earnshaw in the construction of time-keepers, 
no stones have been found sufficiently hard for jewelling 
the holes, except the ruby and the diamond. 
There are several modes of counterfeiting rubies ; 
and some persons have succeeded so well in imitating 
these stones, that even the most able lapidaries, till they 
try the hardness, may be deceived. 
55- The ORIENTAL AMETHYST is an extremely rare 
gem, usually of purple colour, apparently formed by an 
union of the colouring matter of the sapphire and the 
ruby. This stone, if heated, loses its colour, and be- 
comes transparent. After this process its brilliancy is 
such that it is scarcely distinguishable from the dia- 
mond ; and, in jeweller's work, it is occasionally sub- 
stituted for that gem. The common amethyst (79), or 
that which is chiefly seen, is nothing more than a violet- 
coloured rock crystal (78). 
56. The ORIENTAL TOPAZ and EMERALD are each, 
varieties of the oriental ruby, the former straw-coloured, 
and the latter green. This kind of emerald is imported 
from Pegu, and some other parts of the East Indies, 
and is an extremely rare gem. 
57. The SPINEL find BALA1S RUBYare two kinds of 
precious stones, which differ from each other principally in 
colour, the former being of a carmine, and the latter a cochi- 
neal red. 
They vary from the oriental ruby (54) in Icing less hard ; 
in the primitive form of their crystals being regular octa- 
hedrons (fiig- 5), and in their not being much more than $ 
limes heavier than water. 
