Jargon is a varietal and trade name for pale yellow, near-colourless or smoky brown zircon, used historically in European mineralogy and in the gem trade and surviving today as a niche descriptor. The spelling Jargon is the older form; the variant Jargoon is sometimes encountered in nineteenth-century English-language texts. Both names refer to the same material and have been applied somewhat inconsistently across two centuries.

Definition

Zircon, the mineral species ZrSiO4, is one of the oldest minerals known on Earth and occurs in colours including red, orange, brown, yellow, blue, green and colourless. The name jargon was applied historically to zircon in its pale yellow, straw-yellow, near-colourless or smoky-yellow appearance, distinguishing it in older trade usage from the red varietal known as hyacinth and from the blue heated material that became dominant from the early twentieth century onward.

Etymology

The name is recorded in European mineralogy from the eighteenth century. Its derivation is uncertain, with one tradition tracing it to the Persian zargun, meaning gold-coloured, and another connecting it to Italian giargone or French jargon, descriptive terms for an unfamiliar speech and by extension for an unidentified or unfamiliar stone. The Persian zargun is also the most commonly cited etymology for the modern mineral name zircon itself.

Properties

Pale yellow zircon as represented by the jargon name shares the optical and physical properties of zircon as a species. It has a refractive index of approximately 1.92 to 1.98, a hardness of 6 to 7.5 on the Mohs scale, and very high dispersion of around 0.039, second only to diamond among the natural transparent gem materials commonly used in jewellery. The stone takes a brilliant cut well and shows a characteristic strong fire under direct light.

Most natural zircon contains some thorium and uranium, present at trace levels in the crystal structure and responsible over geological time for partial radiation damage that disorders the lattice. Stones with significant lattice damage are termed metamict or low-type zircon, with reduced refractive index and density relative to high-type or normal zircon. Pale yellow jargon material is generally of high or intermediate type with sharp double refraction visible through the table.

Sources

Jargon, like zircon generally, has been recovered historically from Sri Lanka (Ceylon), Burma, Thailand, Cambodia and Madagascar. Sri Lankan stones are the most often associated with the older European jargon trade and were imported through the Dutch East India Company and later channels. Cambodian zircon, particularly the heated blue material from Ratanakiri, has been the dominant source for the modern blue zircon trade.

Use in Jewellery

Jargon was used in eighteenth and nineteenth-century European jewellery as a less expensive substitute for white diamond, particularly in cluster mountings, brooches and earrings of the eighteenth century. The high refractive index and strong fire make jargon visually arresting in mounted form, and well-cut stones can resemble diamond at first glance. Antique jargon jewellery is therefore sometimes encountered with stones that have been historically mistaken for old-cut diamond.

The trade has largely abandoned the term jargon in favour of the species name zircon for clarity and to distinguish the natural stone from the synthetic cubic zirconia, which is unrelated. The historic name nevertheless persists in mineralogical literature, in older auction catalogue descriptions and in the conservative usage of some antique-jewellery dealers.

Distinction from Other Terms

It is important to distinguish three distinct historical uses of related names in the trade. Jargon refers to pale yellow zircon. Hyacinth refers to red, orange or brown zircon, and is a separate historical trade name. Starlite is a twentieth-century trade name for blue heated zircon, principally from Cambodia. All three are zircon and share the species properties.