Why Do We Call Very Dark Things Jet Black?

After all, how much more black could something be? And aren’t jets typically silver in color?

Turns out that the “jet” in this case doesn’t refer to an airplane, but rather a tree—an extremely old tree of the Araucariaceae family that was buried under sediment in ancient seas during the Jurassic Period and fossilized.

After millions of years of high pressure decomposition, the wood turned into a hard dark-black “mineraloid” that was capable of being polished to a high, shiny luster. Jewelry made of jet gemstones was very popular in Victorian England, both as a way to ward off evil and as a symbol of mourning.