Several other common subtypes of uranium glass have their own nicknames: Custard glass (opaque or semiopaque pale yellow) Jadite glass (opaque or semi-opaque pale green; initially, the name was trademarked as "Jadite", although this is sometimes over-corrected in modern usage to "jadeite") Depression glass (transparent or semitransparent pale green). Burmese glass (opaque glass that shades from pink to yellow) Like "Vaseline", the terms "custard" and "jad(e)ite" are often applied on the basis of superficial appearance rather than uranium content. Conversely, "Depression glass" is a general description for any piece of glassware manufactured during the Great Depression regardless of appearance or formula. History Pre-industrial usage The use of uranium glass dates back to at least 79 AD, the date of a mosaic containing yellow glass with 1% uranium oxide found in a Roman villa on Cape Posillipo in the Bay of Naples, Italy, by R. T. Gunther of the University of Oxford in 1912. Starting in the late Middle Ages, pitchblende was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now Jáchymov in the Czech Republic), and was used as a coloring agent in the local glassmaking industry. Martin Klaproth (1743–1817), who discovered uranium, later experimented with the use of the element as a glass colourant. Usage Glass fabrication Uranium glass is used as one of several intermediate glasses in what is known to scientific glass blowers as a 'graded seal'. This is typically used in glass-to-metal seals such as tungsten and molybdenum or nickel based alloys such as Kovar, as an intermediary glass between the metal sealing glass and lower expansion borosilicate glass. Modern production Uranium glass became popular in the mid-19th century, with its period of greatest popularity being from the 1880s to the 1920s. The first major producer of items made of uranium glass is commonly recognized as Austrian Franz Xaver Riedel, who named the yellow () and yellow-green (German: Gelb-Grün) varieties of the glass "annagelb" and "annagrün", respectively, in honor of his daughter Anna Maria. Riedel was a prolific blower of uranium glass in Unter-Polaun (today Dolni Polubny), Bohemia from 1830 to 1848. By the 1840s, many other European glassworks began to produce uranium glass items and developed new varieties of uranium glass. The Baccarat glassworks in France created an opaque green uranium glass which they named chrysoprase from its similarity to that green form of chalcedony. At the end of the 19th century, glassmakers discovered