blue John

== English == === Alternative forms === bluejohn, blue john, blue-john, blue-John, Blue John === Etymology === From blue + John. === Pronunciation === (UK) IPA(key): /ˈbluː dʒɒn/ === Noun === blue John (uncountable) (obsolete, brewing) Afterwort, partially fermented wort. [17th–19th c.] A semiprecious mineral mined in Derbyshire, a form of fluorite with bands of a purple-blue or yellowish colour. [from 18th c.] (US regional) Skimmed milk. [from 19th c.] ==== Related terms ==== sky blue