and Sapphires are scientifically the same stone, differing only in
color. Corundum, the predominating mineral of both, is composed of
nearly pure alumina. The coloring substance which differentiates rubies
and sapphires is believed to be chromium. In the scale of
hardness the gem ranks as No. 9 and is thus the hardest of all
substances excepting the diamond. Color is the most important factor in
determining the value of the ruby. The gem is always more or less
imperfect, but its freedom from bad imperfections is also important.
Since fine rubies of all sizes are extremely rare, the price increases
very rapidly with an increase in size, and a fine ruby of more than
four carats commands an extraordinary price and can be said to be the
most valuable of all gems, exceeding greatly a diamond of equal weight.
A ruby of eleven carats is reported, some twelve years ago, to have
been sold for #80,000, but this is almost the limit of size in which
rubies are ever found. The color varies from the lightest