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(named after the village of Kersanton in Brittany, France), a veined magmatic rock consisting of biotite (comprising about one-third of the rock), quartz, and acid plagioclase, and sometimes also magnetite and apatite. There are varieties of kersantite which, in addition to biotite, contain a small amount of pyroxene and amphibole. The kersantites are genetically associated with granites and rocks similar to them. The difference between kersantites and granites is caused by the processes of differentiation and assimilation.