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A plutonic rock of nepheline and 30-60% mafic materials, generally sodic pyroxene, with accessory apatite, sphene, calcite, and titaniferous garnet.



(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.

References in periodicals archive ?
Prominently on display in the ROM's petrology collection room, this specimen of orbicular ijolite inevitably garners the comment, "What in the world is that?
The circular patterns in this piece of ijolite are called orbicules --circular or ovoid structures that grow in concentric shells around a central core.
Why he chose it: When this specimen first came to the ROM as a donation from the Ontario Geological Survey in 1982, Vertolli thought there must be some mistake in its identification as orbicular ijolite.