Kaolin
3 of the 6 encyclopedias on this shelf carry an entry for Kaolin. All 3 are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
ka'o-lin, a kind of potter's clay. The name is derived from the Chinese Kaoling, meaning lofty hill. Kaoling is the name of a particular hill in China from which large quantities of porcelain clay are dug. All such clays, wherever found, are now called kaolin. It is derived from rock that has disintegrated without having been disturbed. The particles are flattish like scales and do not work in the fingers, that is to say, are not plastic like putty. Kaolin is free from grit. China ware, Japanese ware, Sevres wares, Dresden China, English ironstone china; in short, all the chinaware of the world is made from kaolin. It is akin to chalk. Valuable deposits are rare. Kaolin is mined in Alabama, Georgia, Massachusetts, North Carolina , South Carolina , Florida, and several other states; but we still import about 100,000 tons of superior kaolin each year for our chinaware factories. See Clay ; Pottery ; Porcelain
The Encyclopedia of Founding (1892)
A pure white clay resulting from the decomposition of feldspar in granitic rocks. The materials employed by the Chinese for the manufacture of porcelain are known to be kaolin, petuntze, or quartz reduced to a fine powder; and the ashes of fern, which contain potassic carbonate. Kaolin is used extensively for the manufacture of clay crucibles for steel melting, being mixed with equal quantities of Stourbridge clay and some old pot and coke-dust. See CRUCIBLE; FELDSPAR.
Collier's New Encyclopedia (1921)
or KAOLINITE, a mineral element found in granite, and generally arising from the decomposition of the felspar. It is essentially a hydrated silicate of alumina. After being levigated, it is extensively used in the manufacture of porcelain, and is hence called China clay. The name kaolinite was applied by Johnson and Blake to a soft powder made up of minute, transparent, pearly scales, which is always present in greater or lesser quantity in all kaolin.
What Has Changed in the Last Century
The mineralogy in these entries holds up: kaolinite is indeed a hydrated aluminium silicate formed by the decomposition of feldspar, though its layered atomic structure was only worked out by X-ray methods from about 1930, and Aiton's remark in 1910 that kaolin is "akin to chalk" would not be written today, chalk being calcium carbonate. What has really moved is what the clay is for. Aiton's tally of chinaware -- "Sevres wares, Dresden China, English ironstone china" -- covers only a small fraction of modern demand: the largest single use of kaolin now is as a coating and filler for paper, with paint, rubber, plastics and ceramics taking most of the rest. Georgia, listed by Aiton as one state among several, became the centre of a kaolin belt that made the United States a leading producer and exporter rather than the importer of "about 100,000 tons of superior kaolin each year" he described.
Written for this edition, 2026.