Friday, February 8, 2008

Jet aka Black Amber

Last year my eight year old Border Collie had to be put to sleep, it was discovered that he had a tumour on his spine after not being able to get up one morning. This post is in memory of my beautiful boy, Jet.

So what is Jet exactly? It measures 2.5-4 on the Mohs scale and is one of the softest semi-precious stones, most other minerals can scratch it. It is way too soft to be facet cut, so the most common form of cut is either 'en cabochon' or made into beads. It was used in Britain long before the Romans arrived and is said to have been found in 4500 year old Bronze Age Barrows in Yorkshire and Scotland.

There's an example in the pic below. These were sold to me as Jet beads and are featured with Ernite. Question is now, are they really Jet? Possibly, but certainly not Victorian Jet.

The interesting thing about Jet is that is was once alive, in the form of a tree.
Originally it come from a weird species of Conifer that had a banded spiked trunk, and cones the size of a football. Today the tree's formal name is "Araucaria".

In Australia, the Hoop and Bunya Pines are of that species. For those of us who have seen the Bunya Pine which mainly grows in South East Queensland, we are in awe of the size of its cones which can grow to the size of a football. However I digress.

It was probably due to something as dramatic as climate change, that these ancient trees died by the forest full. Massive logs and debris built up in swampy areas as these giants crashed to the ground, they were then covered with mud, causing them to fossilise without air, shrinking to a black layer of Jet, probably just a few centimetres thick. Directly above this a layer of limestone formed, which then became covered with silt, shale and clay.

Jet was made famous initially by Queen Victoria. Her Jet came from the Whitby mines in Yorkshire. Whitby Jet is considered the finest in the world although very good quality genuine Jet is found all over Europe and North America, especially Spain, Germany and Pennsylvania.

Now back to Queen Victoria, she chose to wear Jet as her grieving adornment when her prince consort passed away. Black signifies the "absence of light" and known to be the colour of death in the Western world. Due to Queen Victoria, Jet became the height of fashion, everyone wore it, its beads were easy to wear with woman's clothing styles of the day. However, Jets popularity diminished around the 1880's when Victoria took to wearing white stones, such as pearls and diamonds.

I've read recently that you should never loan out your Jet jewellery, as it is said to be so absorptive that its owner can be vulnerable to negative magic if it falls into the wrong hands.

Some interesting facts about Jet

When warmed it attracts lint, it can support innate heat, and this can cause it to spontaneously combust.

Testing for real Jet

You can try the scratch test. Use a porcelain tile and scratch the Jet against the rough back of the tile, it should leave a chocolate brown mark. Coal which is softer will leave a black mark, Glass a white mark and Vulcanite (a primitive form of plastic) a trail of grey. It is said that when manufacturers of fake jet realised this they started to add a brown dye to the surface plastic.

Some facts about Vulcanite from the Plastics Historical Society

Combining natural rubber with sulphur in a furnace, Vulcanite was discovered in the USA in 1839 by Charles Goodyear, patented by Hancock in England in May 1843 and Goodyear in USA in June of the same year.

Various mouldings in Vulcanite were exhibited at the Great Exhibition of 1851.

The material, most commonly black in colour was used to make combs, buttons, jewellery, fountain pens, pipe stems (both plain and decorative), musical instruments, etc. It was also widely used as an electrical insulator and for chemically resistant linings. A reddish colour was used for denture plates until superseded by celluloid and acrylic. Then in 1930 a reddish material rippled with black was popular for fountain pen and pencil barrels. Since the 1930s however Vulcanite has been based wholly or partly on various synthetic rubbers rather than natural rubber.

An example of Vulcanite

So today the best test for Jet is to heat a needle and hold it to the back of the piece. If its real nothing will happen, plastic will bubble and smell. A more dramatic and of course destructive test is to hold the Jet in a flame where it will give off a greenish flame with sooty smoke, plastic will just melt. Make sure you wear safety glasses and use tongs, because if the Jet you're testing is Glass it will certainly explode.

Ok so now I'm off to test one of my Jet Beads, so which test will I use...humm. I'll let you know the outcome.

Ed.. ok it could be Jet I used the porcelain scratch test and it left a choc brown line, but is might also be dyed plastic. So will try the heat test next.

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