DI'ORITE (front Gk. StoplOtv, diorizcin, to distinguish. from Sal, dig, through + dplrem hori.:eia, to divide. from opoc., ho•os, An igneous rock of granitie texture. the essential constituent minerals of which arc a lime-soda feldspar and either hornblende or dark mica, or both of these minerals. Tim average chemical composition of diorite is about as follow,: Silica, ril per cent.: alumina. 10 per vent.: ferric oxide, 3 per cent.; Ferrous oxide.:; per cent.; magnesia, 4 per cent.: lilac. 11 per ; soda. :3 per cent.; potash. 2 per cent. Alany rocks formerly classi fied as diorites are now by many writers sopa rated because of peeuliarities of texture and of manner of occurrence: e.g. kersantite. camptom tile, aphanite. etc. In addition to lime-soda kid spar. hornblende, or mien, diorites may contain quartz. alkali feldspar, or angite, and other minerals in smaller quantities. .bearding to the
Presence or absence of quartz. diorites are classi fied as quartz diorites or diorites proper. Each of these groups is subdivided into ntiea (1 iorite-, hornblende diorites, or angite diorites. as mica, hornblende, or augite predominates among the !la rkcr minerals. Peculiarities Of tex ture alone serve to distinguish quartz diorite: from 41:icites (q.v.), and diorites front andesites (q.v.), the composition being essentially the Chemically. diorites differ from granites chiefly in containing less silica and potash and more lime. magnesia, and they are distinguished by the greater almuffinne of lime—oda feldspar and by the darker color. due to the greater abundance of mien and horn blende. Diorite is often quarried for use as stone.