The red sapphire or ruby is the most valuable of the corundum family,
and when found of a good color, pure and brilliant, and in sizes of one
carat and larger, it is much more valuable than a fine diamond of the
same size.
Fine rubies larger than 1½ to 2 carats are very rare, and when a fine
stone from 3 to 5 carats is offered for sale, the price mounts into the
thousands.
The color varies from the lightest rose tint to the deepest carmine;
that color, however, which has the greatest value is known in commerce
as pigeon’s blood, and is the color of arterial blood, or of the very
centre of the red ray in the solar spectrum.
The imperfections in rubies, as in all corundums, consist largely of
clouds, milky spots, and cracks. A perfect ruby is rarely met with,
and a stone possessing brilliancy and the true color, even if slightly
defective, is considered more valuable than an absolutely perfect ruby
of an inferior color.
Rubies are found in Siam, Ceylon, Burmah, Brazil, Hindustan, Borneo,
Sumatra, Australia, France, and Germany.
Where rubies and sapphires are met with it is said that gold is almost
sure to be present.
Chemists have succeeded in producing minute crystals of rubies
and sapphires which, under the microscope, presented the true
crystallization of corundums, and upon being tested proved to be of the
same hardness as rubies and sapphires; but these specimens were small,
and cost very much more to produce than their commercial value.
Ruby spinels, garnets, hyacinths, red quartz, burnt Brazilian or rose
topaz, and red tourmaline are sometimes passed off for the ruby.
The true ruby will scratch all of these stones readily, the spinel
is lighter in specific gravity, and has generally a slight tinge of
yellow, even in the most pronounced red specimens.
The ruby will turn green under the flames of a blow-pipe, but when
cooled off, resumes its original color.
The garnet and topaz are easily scratched by the ruby, the hyacinth is
heavier, and quartz and tourmaline lighter than the ruby. Some
so-called reconstructed rubies, recently offered for sale, are of a
very fine color, and closely resemble the Oriental gems.
The hardness and specific gravity are the same, but they differ in one
very important point, namely: they lack the brilliancy of the true
ruby. In addition to this lack of fire, a microscopical test discloses
formations which will distinguish the manufactured from the natural
stone.