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(from Ijo, the Swedish name for the Finnish village of Ii, and Greek lithos, “stone”), a noncrystalline igneous rock composed mainly of nepheline (52 percent), pyroxene (40 percent), and accessory minerals such as apatite, sphene, and calcite. With increasing nephelene, ijolite is transitional into urtite. Ijolite forms large masses and dikes genetically associated with nepheline syenite. It is found in the USSR in the Khibiny, Siberia, and the Uzbek SSR; abroad it is found in Finland, Norway, Sweden, and southern and eastern Africa.