Today’s Arbor Day! The day to celebrate trees and their many gifts to humankind.¬†Everyone knows they produce amber, even if it is over the course of millions of years. Not everyone knows that they are also the source of the black gemstone jet.

Jet differs from a lot of gemstones because it’s not actually a rock. It’s one of the few gemstones made from plant material. Amber is made of resin, usually from evergreens, which is produced by a plant, so it doesn’t get that distinction. Jet is created by wood, usually evergreens, decomposing under very specific conditions.

Hard jet is formed when that wood decomposes under high pressure submerged in stagnant salt water. Soft jet is made the same way as hard jet, but needs fresh water instead of salt. Jet is actually a form of lignite, or brown coal. Just like coal, jet can and will burn and is soft enough to leave streaks behind when scratched on unglazed porcelain. Because it’s so soft, it’s generally worn encased in metal to protect it from other pieces of jewelry. However, this allows it to be carved more like clay than stone, so jet is one of the more versatile of the gemstones.

Image of 19th century jet brooch, usually worn in mourning

Jet has a long history of use as jewelry, dating back to 10,000 BCE during the Neolithic period. Britain is renowned for its high quality of jet that’s been used in jewelry since the Roman era. It was used in pins, bracelets, pendants, anything you can think of. Romans saw it as a means of protecting themselves from all sorts of negativity, so it was popular all throughout the empire. It became the height of fashion during the Victorian Era, when Queen Victoria wore jet to mourn the loss of her husband, Prince Albert. Ever since, jet has been associated with mourning and religion.

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