Jargoon or jargon (occasionally in old writings jargounce and jacounce) is a name applied by gemologists to those

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...

s which are fine enough to be cut as

gemstone A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, ...

s, but are not of the red color which characterizes the ''hyacinth'' or

jacinth Jacinth (, ) or hyacinth () is a yellow-red to red-brown variety of zircon used as a gemstone. In Exodus 28:19, one of the precious stones set into the '' hoshen'' (the breastplate worn by the High Priest of Israel) is called, in Hebrew, '' les ...

. The word is related to Persian ''zargun'' (zircon; ''zar-gun'', "gold-like" or "as gold"). Some of the finest jargoons are green, others brown and yellow, whilst some are colorless. The colorless jargoon may be obtained by heating certain colored stones. When zircon is heated it sometimes changes in color, or altogether loses it, and at the same time usually increases in density and brilliancy. The so-called ''Matura'' diamonds, formerly sent from Matara (or Matura), in

Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...

, were decolorized zircons. The zircon has strong refractive power, and its lustre is almost adamantine, but it lacks the fire of the diamond. The

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its dens ...

of zircon is subject to considerable variation in different varieties ; thus Sir

A. H. Church A is the first letter of the Latin and English alphabet. A may also refer to: Science and technology Quantities and units * ''a'', a measure for the attraction between particles in the Van der Waals equation * ''A'' value, a measure of ...

found the specific gravity of a fine leaf-green jargoon to be as low as 3.982, and that of a pure white jargoon as high as 4.705. Jargoon and

tourmaline Tourmaline ( ) is a crystalline Silicate mineral, silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is a gemstone and can be found in a wide variety o ...

, when cut as gems, are sometimes mistaken for each other, but the specific gravity is distinctive, since that of tourmaline is only 3.103. Moreover, in tourmaline the

dichroism In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), or one in which light rays having different polarizations are abs ...

is strongly marked, whereas in jargoon it is remarkably feeble. The

refractive indices In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

of jargoon are much higher than those of tourmaline.

References

Kunz: Gems and Precious stones of North America; Zircon

External links

{{EB1911, wstitle=Jargoon Gemstones Zirconium minerals