prefix, repr. Gr. ἐπι- (before an unaspirated vowel usually ἐπ-, before an aspirated vowel ἐφ-, represented in Eng. by EP-, EPH-), used in prepositional and advb. senses, ‘upon, at, or close upon (a point of space or time), on the ground or occasion of, in addition.’
1. In words derived from compounds that either were, or might legitimately have been, formed already in Greek. Also in mod. scientific terms after the analogy of words derived from Gr.; chiefly with sense ‘placed or resting upon,’ as in epicalyx, epicorolline.
2. In mod. Chemistry employed in the names epibromhydrin, epichlorhydrin, epicyanhydrin, epiiodohydrin, denoting substances of analogous composition belonging respectively to the bromhydrin, chlorhydrin, etc., series. They contain one equivalent of a salt-radical with 3 of carbon, 5 of hydrogen, and 1 of oxygen.
3. In Mineralogy prefixed to the names of certain minerals to form names of other minerals closely resembling them in composition, as in Epiboulangerite, a sulph-antimonide of lead resulting from the decomposition of boulangerite. Epichlorite, a hydrous silicate of aluminium, iron and magnesium. Epidiorite, a mineral differing from diorite in that the hornblende it contains is fibrous. Epistilbite, a zeolitic mineral, a hydrous silicate of aluminium, calcium and sodium.
1872. Dana, Min., 1st App. 5. Epiboulangerite.
1850. Dana, Min., 263. Epichlorite … fuses only in thin fibres and with difficulty.
1879. Rutley, Study Rocks, xiii. 245. The viridite (chlorite, epichlorite, or chloritic matter).
1887. Dana, Manual Min., 482. Epidioryte consists of plagioclase with hornblende, some quartz, a little orthoclase, and some pyroxen.
1826. Edin. Jrnl. Sc., IV. 286. The cleavage of epistilbite is quite perfect.
