Jet: Proper Use and Identification
inDecember 26, 2007 - 12:44am
While a number of jewelry materials can be described as, “Black as jet”, the word ‘jet’ should only be used to describe an item of jewelry which is made from the organic material identified as 'jet' to avoid any possible confusion on the part of the buying public.
Jet is one of the oldest materials used in making jewelry. Bronze age tombs have been unearthed that contained jet ornaments and jewelry. The Roman occupation and Viking conquests of Britain saw to it that the material was widely distributed. The Whitby area, near York, is the best-known source for jet in the world.
Jet is an organic material or mineraloid – a fossilized form of vegetation. Due to is high carbon content it is classified as coal. Some sources believe jet is a lignite coal, but others disagree asserting jet to be a fossilized by product of the decomposition of a particular species of tree, the Araucaria. While used since ancient times for ornaments and jewelry, it reached its height of popularity during the Victorian era. The majority of 19th century jet jewelry was produced in Whitby in Yorkshire, England. The Whitby jet industry showcased its products at the Crystal Palace exhibition in 1851, securing a place in the fashion world for this unusual material. With the death of Prince Albert in 1861, and the subsequent popularity of mourning jewelry and requisite black color insured that jet would be quite fashionable for years to come. Jet is lightweight making it an excellent choice for the very large jewelry designs that were in-style at the time. Jet is also easy to carve and because it can be turned on a lathe, it was an ideal material for bead production.
There are a number of materials, which are easily confused with jet, many of which saw widespread use during this time period. Bog oak exhibits many of the same qualities as jet, thus giving is a similar appearance to jet, and is actually a related material. As vegetable matter decomposes, it becomes peat, a material that is required to create the conditions necessary to preserve (petrify) large trees to produce bogwood. The heat and pressure of several million more years is needed for the material to change into the coal known as jet. Bog oak pieces can be carved like jet, or molded.
Gutta-percha and vulcanite are two man-made materials, which were also used to simulate jet, offering buyers a cheap alternative to genuine jet. Gutta-percha is a rubbery substance derived from the latex material of several varieties of tropical trees. Vulcanite is hard rubber produced by a process called vulcanization. Both materials are molded and never cut like jet. Items made from jet have sharper details than items produced from gutta-percha or vulcanite.
‘French Jet’ or black glass is another material sometimes misidentified as jet. Black glass is much heaver than jet, has a cold feel and during the Victorian period was used primarily for the necklaces. Opaque black minerals like chalcedony (black onyx) and organics such as black coral can also be mistaken for jet, although they too are heavy and cold to the touch. Dyed horn is another material that can be misleading.
CHARACTERISTICS AND TESTS
True jet is lightweight. Finished pieces characteristically have sharp precise cuts. If subjected to a hot point (though not recommended) it will give off an oily or coal like odor. When rubbed with wool it will develop an electrical charge, similar to amber. The most definitive test is its streak. When rubbed against an abrasive surface, it will leave a brown streak. This is also a somewhat destructive test, which must be used with great caution. There are no known enhancements of jet.
Gutta-percha will give off a burnt rubber smell when rubbed briskly. It and vulcanite will give off the same smell when subjected to a hot point test. Vulcanite may also have a sulfurous smell, as sulfur is one of the materials used in its production. Horn products will give off the smell of burnt hair when subjected to a hot point, and sometimes when rubbed briskly.
Please note that the hot point test, along with streak testing, can be destructive tests. Extreme caution must be used to avoid damage to the pieces being tested.
Jet will warm to the touch quicker than black glass (French Jet), and both materials will warm to the touch quicker than a mineral like chalcedony.
New jet jewelry pieces are still being produced, but its last extensive use was during the 1920’s and 30’s as beads for “flapper” jewelry.
While almost synonymous with the word black, great care must be used when using the term jet as a color description. A buyer might expect those “Jet Black Beads” to actually be made of jet. If you really feel the overwhelming need to use the term 'jet' as a color description, please take the extra time to make sure your meaning and description are clear, by using phrases like “Jet Black Colored Glass Beads”. Similarly, it should be made clear that “French Jet” pieces are “French Jet Glass”. The best way to avoid confusion is to only use the word ‘jet’ when describing the organic material for which Whitby England is famous.