Ijolite
“Nepheline and pyroxene from alkaline depths”
Ijolite is a rare, coarse-grained intrusive igneous rock composed mainly of nepheline and aegirine-augite. It's the plutonic equivalent of nephelinite and forms in highly alkaline magmatic complexes, often associated with carbonatites and other unusual rock types.
nepheline, aegirine-augite, titanite, apatite, melanite garnet, calcite
Iivaara (Finland — type locality), Alnö (Sweden), Magnet Cove (Arkansas, USA), Kola Peninsula (Russia), Phalaborwa (South Africa)
5.5-6
Ijolite is named after Iivaara (historically 'Iijoki') in Finland, and it almost always occurs in ring complexes where it forms alongside some of the rarest and most exotic rock types on Earth.
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Why does ijolite almost always occur alongside carbonatites in alkaline ring complexes?
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