IJOLITE, in petrology an igneous rock composed essentially of nepheline and an alkaline pyroxene, usually aegirine-augite. The rock was originally described from Russia where it occurs in various parts of the Kola Peninsula. Typically the pyroxene is well crystallized, the nepheline allotriomorphic. Accessory minerals include melanite-garnet, titanite, apatite, cancrinite and calcite. This rock is the plutonic equivalent of the volcanic nephelinites and hypabyssal nepheline dolerites. I j olites are also known from Norway (Fen district) and British Columbia (Ice river), but they are quite rare. The rocks known as urtite and melteigite are essentially similar assemblages. In the former nepheline largely preponderates, while melteigite is a melanocratic variant with excess pyroxene. (C. E. T.)