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

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 th ...

s that are of sufficient quality to be cut as

gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...

s, but not the red color that characterizes the ''hyacinth'' or jacinth. The word is related to Persian (zircon; ''zar-gun'', "gold-like" or "as gold"). Some of the finest jargoons are green, others brown and yellow, while some are colorless. The colorless jargoon may be obtained by heating certain colored stones. When zircon is heated it sometimes changes color, or 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, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

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

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of zircon is subject to variation in different varieties; thus Sir A. H. Church 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 chemical compound, compounded with chemical element, elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a ...

, when cut as gems, are sometimes mistaken for each other, but the specific gravity is distinctive, since 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 (optics), dispersion), or one in which light rays having different P ...

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

refractive indices In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

of jargoon are much higher than those of tourmaline.

References

Sources

Kunz: Gems and Precious stones of North America; Zircon

External links

* Gemstones Zirconium minerals {{gemology-stub