What is Jet?
Millions of years ago, during the Jurassic period, carboniferous forests grew in this part of England. One of the most prominent trees was one similar to our modern day Araucaria, or Monkey Puzzle tree. These large trees would either die and get washed into the sea, or be carried to the sea during violent storms where they would become waterlogged and sink to the bottom of the ocean not far from shore. As the millennia passed, silt and sand encased these logs, compressing them into what is now known as Jet.
Jet is a form of Lignite, which is a variety of coal. Jet, though considered lignite, is more dense than common lignite, and though soft (2.5-4), can take a nice polish. Jet is found throughout the world in various areas, but the Jet from the area of Whitby, England specifically, is a true black jet with few inclusions, and can be easily worked on a lathe or in carvings.
Pictured: Antique Jet Cameo