Physical Characteristics and Composition of Zircons

THE ZIRCON:

The zircon, called also the jargon, is altogether special in its composition, being formed of silica, united with a peculiar mineral--zircona, the oxide of zirconium.

The zircon crystallizes in four-sided prisms, with various modifications. Fig. 77 shows the primitive form, and Fig. 78 a modification approaching the form of the dodecahedron.

Generally speaking, each of the two types has its own particular colour, which is shared by the crystals belonging to it. The first is a brownish and greenish-yellow, the second brownish-red. Werner called the rhomboidal type hyacinth, and the prismatic zircon. Ancient lapidaries made the same distinction, and the stone that Werner calls zircon is their jargon of Ceylon.

The colourless crystals of the zircon are the most valued. They take on an excellent polish, display an adamantine lustre and fire, and will pass for diamonds if not too closely inspected. The zircon, accordingly, is sometimes introduced into ornaments, and sold to inexperienced people as a diamond, a particularly gross fraud, inasmuch as the zircon has but a very trifling value. Indeed even an exceptional zircon, of a beautiful olive-green tint, of the dimensions shown in Fig. 79, was sold at the auction of M. Dree for the sum of $16. A diamond of the same dimensions, even if only a rose, would weigh about 5 carats, and would bring not less than $1800.