Ijolite


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ijolite

[′ē·ə‚līt]
(petrology)
A plutonic rock of nepheline and 30-60% mafic materials, generally sodic pyroxene, with accessory apatite, sphene, calcite, and titaniferous garnet.

Ijolite

 

(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.
So not only is this specimen rare, it may very well be the only example of an orbicular ijolite in the world.
Urtite there contains numerous xenoliths of fine-grained titanite-rich ijolite rock.
1) Melteigite is a dark colored plutonic rock that is part of the ijolite series and contains nepheline and 60-90% mafic minerals, especially green pyroxene.
2) Ijolite refers to a series of plutonic rocks containing nepheline and 30-60% mafic minerals, generally clinopyroxene, and including titanite, apatite and sometimes andradite (Jackson, 1997).
Urtite: A light-colored member of the ijolite series that is composed chiefly of nepheline and 0-30% mafic minerals, especially aegirine and apatite.