Missourite
“Leucite-rich plutonic rarity”
Missourite is one of the rarest plutonic rocks on Earth — a coarse-grained intrusive rock dominated by leucite and clinopyroxene with little to no feldspar. It represents the plutonic equivalent of leucitite and forms only from extremely potassium-rich, silica-poor magmas.
leucite, augite (diopsidic), olivine, phlogopite, magnetite, apatite, perovskite
Highwood Mountains (Montana, USA — type locality), Bearpaw Mountains (Montana), very few other localities worldwide
5-6
Missourite is so rare that the Highwood Mountains of central Montana remain virtually the only well-documented occurrence — making this remote range one of the most unusual igneous complexes on the planet.
Test Your Knowledge
The presence of leucite instead of feldspar in missourite indicates what about the magma's silica content?
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