Origin
Jet is a product of high pressure decomposition of wood from millions of years ago, commonly the wood of trees of the family Araucariaceae. Jet is found in two forms, hard and soft. Hard jet is the result of the carbon compression and salt water; soft jet is the result of the carbon compression and fresh water.
The jet found at Whitby, England is of early Jurassic (Toarcian) age, approximately 182 million years old.
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