Theralite

Theralite occurs, for example, at Lugar Sill, Scotland, and at the Crazy Mountains, Montana. == Teschenites ==

Teschenites were once considered part of the theralite group. They contain essential pyroxene, olivine and analcime rather than nepheline. Modern petrology would classify the teschenites as an analcime-bearing gabbro. They are petrogenetically unrelated to nepheline gabbros as analcime is not produced by the same genetic processes. == Essexites ==

Essexite is a form of silica-undersaturated pyroxene gabbro, containing nepheline and orthoclase as essential constituents, though often in small proportions. Essexites can be considered to represent the intrusive equivalent of an alkaline basalt. Essexites are usually associated with other alkaline, silica undersaturated to monzonitic intrusive rocks and coeval high-alumina basalts. Essexites are no longer considered part of the theralite group and are more properly known as nepheline monzogabbro or nepheline monzodiorite. The presence of orthoclase indicates a petrogenetic difference with nepheline gabbros. ==References==