true ruby in brightness of color and when held up
to the light show more prismatic colors than the true ruby, owing to the
greater dispersion of garnet. The color also lacks variety (owing to
lack of dichroism). While a fine garnet may make a fair-looking "ruby"
when by itself, it looks inferior and dark when beside a fine ruby. By
artificial light, too, the garnet is dark as compared with the true
ruby, and the latter shows its color at a distance much more strongly
than the garnet.

The red zircon, or true hyacinth, is rare. (Many hessonite garnets are
sold as hyacinths in the trade. These are usually of a brownish red.)
The red of the hyacinth is never equal to that of the ruby. It is
usually more somber, and a bit inclined to a brownish cast. The
dispersion of zircon, too, is so large (about 87 per cent. of that of
diamond) that some little "color-play" is likely to appear along with
the intrinsic color. The luster too is almost adamantine while that of
ruby is softer and vitreous. Although strongly doubly refracting, the
hyacinth shows scarcely any dichroism and thus lacks variety of color.
Hence a trained eye will at once note these differences and not confound
the stone with ruby.

Spinels, when red, are almost always more yellowish or more purplish
than fine corundum rubies. They are also singly refracting and hence
exhibit no dichroism and therefore lack variety of color as compared
with true ruby. Some especially fine ones, however, are of a good enough
red to deceive even jewelers of experience, and one in particular that I
have in mind has been the rounds of the stores and has never been
pronounced a spinel, although several "experts" have insisted that it
was a scientific ruby. The use of a dichroscope would have saved them
that error, for the stone is singly refracting. Spinels are usually
clearer and more transparent than garnets and show their color better at
a distance or when in a poor light.

Tourmaline of the reddish variety (rubellite) is seldom of a deep red.
It is more inclined to be pinkish. The dichroism of tourmaline is
stronger than that of ruby and more obvious to the unaided eye. The red
of the rubellite should not deceive anyone who has ever seen a fine
corundum ruby.

YELLOW STONES

Considering next the stones of yellow color, we have the following
species to deal with: (1) diamond, (2) corundum, (3) precious topaz, (4)
quartz, (5) beryl, (6) zircon, (7) tourmaline.

YELLOW ZIRCO