ZIRCON.

The zircon, hyacinth, jacinth, or jargoon belong to the tetragonal

system of crystallization. The cleavage is imperfect, fracture

conchoidal, and specific gravity 4.4 to 4.7, the stone being much

heavier than any other gems. Its hardness is 7.5 and lustre vitreous to

adamantine, and refraction double to a high degree.

The zircon is phosphorescent when heated; before the blow-pipe it

is infusible, but loses its color; and with borax it melts into

a transparent glass. Sulphuric acid affects this gem after long

maceration.

The composition of the zircon is: zirconia, 66.3; silica, 33.7; with a

trace of peroxide of iron.

Under the microscope, the texture of these gems presents a watery

appearance, called by the French _ratiné_, and which looks like a

liqueur poured into water. This is a strong distinguishing point in the

zircon.

The zircon, hyacinth, jargoon, and jacinth are the same gems but of

different colors.

The brown, violet, and green colors are known as zircons, the red as

hyacinth, the yellow as jacinth, and the grayish-white and white as

jargoons.

The jargoon has often been palmed off as a diamond because of its

transparent color and adamantine lustre.

The zircon is found in Ceylon, Germany, France, Bohemia, America, and

in fact in nearly all parts of the earth, as many as 120 localities

having been noted where specimens of the mineral have been discovered.

The zircon can be distinguished from the garnet by its peculiar

diamond-like brilliancy and its specific gravity.