Jet
3 of the 6 encyclopedias on this shelf carry an entry for Jet. All 3 are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a peculiar form of pitch coal. It is a solid, black, dry, inflammable substance. It occurs as a mineral in veins of lignite coal. When first mined jet may be carved and turned readily into toys, buttons, and articles of ornament. It takes a high polish. The finest jet in the world is found in a vein twenty feet thick at Whitby, Yorkshire. The monastery of Whitby did a thriving business in jet rosaries and crosses when that shrine was a resort of pilgrims. Other fine veins are found in the provinces of Aude, France, and Asturias, Spain. The original jet quarry was in Asia Minor . The Greek name, of which jet is a corruption, was gagates. Jet was prized highly by the ancients and is still the appropriate jewelry of mourning, though cheap imitations in glass render genuine jet ornaments less desirable. Its deep lustrous black has made jet a familiar standard of comparison. Milton speaks of the "pansy, freaked with jet," and Scott, of the black-cock's "jetty wing." See Asphalt
An Encyclopaedia of Occultism (1920)
Its virtues are thus described by Pliny, according to the version of Holland : In burning, the perfume thereof. chaseth away serpents, and bringeth women again that lie in a traunce by the suffocation or rising of the mother; the said smoke discovereth the falling sicknesse and bewraieth whether a young damsel be a maiden or no; the same being boiled in wine helpeth the toothache, and tempered with wax cureth the swelling glandules named the king's evil. They say that the magicians use this jeat stone much in their sorceries, which they practice by the means of red hot axes, which they call axinomancia, for they affirm that being cast thereupon it will burne and consume, if that ewe desire and wish shall happen accordingly." Jet is known in Prussia as black amber.
Collier's New Encyclopedia (1921)
a dense variety of lignite passing by degrees of quality into bituminous fossil wood, sometimes perfectly black, capable of being easily cut and carved, and of receiving a very beautiful polish. It takes its name from Gagas or Gages, a place in Asia Minor, where, according to Pliny, the substance was obtained, whence in his time it was called gagates, afterward corrupted into gagat, the modern German name, and jet. As a material for mourning ornaments jet is admirably adapted, and for that purpose is largely used.
What Has Changed in the Last Century
The mineralogy in these entries still holds, but the trade behind it has all but vanished. Jet is now known to be fossilised wood of an araucarian, monkey-puzzle-like conifer, compressed in the Early Jurassic shales of the Yorkshire coast about 180 million years ago; it does not form the continuous "vein twenty feet thick" Aiton describes in 1910, but scattered thin lenses in the Jet Rock. The Whitby industry that employed well over a thousand people at its Victorian height had collapsed by the time Collier's called jet "largely used" for mourning ornaments in 1921 trade in black mourning dress faded after Queen Victoria's death in 1901, and glass and moulded plastics took the rest. A handful of Whitby workshops still cut and polish jet today, for tourists and collectors rather than for grief.
Written for this edition, 2026.