Jet black is sometimes used as a description, but most people do not get the reference.
An article from CNN suggests Jet is back in favor with designers:
A forgotten gemstone that reigned during the Victorian era comes back into focus
Radiant diamonds, sapphires, and rubies have been among the most coveted gemstones on the planet for nearly a century. But long before their reign, a far less dazzling gem captured the hearts of jewelry lovers — and now it’s making a comeback.
Jet, a flat-black, opaque gemstone derived from wood that has experienced extreme compression over millions of years, was the haute stone throughout the Victorian era, a time when fashion and jewelry deftly signaled a person’s social status, financial wealth and even emotional state. Victorian dress was rife with symbolism and evolved around rigid codes of propriety and caste. Tightly pulled corsets and top hats, to name two ubiquitous items from the era, signified wealth and propriety, while jewels depicting doves hinted to an individual’s deep religious devotion.
Surprisingly lightweight and inky-black, jet is one of the oldest known gemstones, and has been carved and shaped by the artistically inclined since the Neolithic era (7,000-1,7000 B.C.). Both the Romans and Vikings fashioned items with jet, ranging from buttons and rings to tiny sculptures and protective amulets. But it was Queen Victoria who delivered jet to fashion’s highest heights in the mid-1800s. The monarch wore jet often, most notably in the second half of her reign; the gem matched the all-black ensembles she wore exclusively following the death of her husband, Prince Albert. (Jet has been synonymous with mourning dress ever since.)
“Anyone who was anyone was wanting to wear jet in the Victorian era,” said British gemologist Sarah Steele, one of the world’s only jet researchers. “We went around the world looking for sources of jet — to Venezuela, to the north of Spain — and exported it back to the UK.”
Sustained interest in the gem, however, meant the market was slowly flooded with lower-quality jet that chipped and cracked more easily, eroding consumer confidence. Simultaneously, the plastic revolution was accelerating. The popular (and now acutely collectible) jewelry resin Bakelite was invented in 1907, and certain manufacturers even perfected a plastic jet — an effective, if accidental, category killer.
All this led to jet’s popularity plummeting. “Everyone was absolutely sick of mourning, and then the first World War happened, and that was that,” Steele added. “We’re actually lucky the industry survived at all.”