lden
fancies" can be distinguished from other brown stones (except perhaps
brown zircons) by their adamantine luster, and their prismatic play or
"fire."

Brown garnet (hessonite or cinnamon stone), sometimes wrongly called
hyacinth in the trade, is of a deep reddish-brown color. Usually the
interior structure, as seen under a lens, is streaky, having a sort of
mixed oil and water appearance.

Brown tourmaline is sometimes very pleasing in color. It is deep in
shade, less red than cinnamon stone, and with marked dichroism, which
both brown diamond and brown garnet lack.

Brown zircon, while lacking dichroism, is frequently rich and pleasing
in shade, and when well cut is very snappy, the luster being almost
adamantine, the dispersion being large, and the refractive index high.
It is useless to deny that by the unaided eye one might be deceived into
thinking that a fine brown zircon was a brown diamond. However, the
large double refraction of the zircon easily distinguishes it from
diamond (use the sunlight-card method or look for the doubling of the
edges of the rear facets as seen through the table). The relative
softness (7-1/2) also easily differentiates it from diamond.

COLORLESS STONES. Few colorless stones other than diamond, white
sapphire (chiefly scientific), and quartz are seen in the trade.
Colorless true topaz is sometimes sold and artificially whitened zircon
(jargoon) is also occasionally met with. Beryl of very light green tint
or even entirely colorless may also be seen at times.

Such colorless stones must of course be distinguished by properties
other than color. They are mentioned here merely that the learner may be
aware of what varieties of gem minerals occur in the colorless
condition, and that all these minerals also occur with color in their
more usual forms. This does not even except the diamond, which is rarely
truly colorless.

LESSON XV

HOW TO TELL SCIENTIFIC STONES FROM NATURAL GEMS

It should be said first that the only true scientific or synthetic
stones on the market are those having the composition and properties of
corundum, that is to say, the ruby and the several color varieties of
sapphire, as blue, pink, yellow, and white. There is also a greenish
stone that appears reddish by artificial light, which is called
scientific alexandrite but which has, however, the composition and
properties of the corundum gems rather than those of true alexandrite.
All so-called "s