Montgomeryite

Montgomeryite is a calcium magnesium aluminum phosphate hydrate and the magnesium analogue of kingsmountite. It forms monoclinic, colorless, yellow, red, green to dark green, transparent to translucent, prismatic, lath-like and flattened on {010}, elongated and striated along [001] and terminated by pyramids {010}. Also found as massive, subparallel aggregates of coarse plates.

Montgomeryite was named in 1940 for Arthur Montgomery, Mineralogist and Professor of Geology, Lafayette College, Easton, Pennsylvania, USA, who collected the first specimens. It occurs as a secondary mineral in sedimentary phosphate nodules at the type locality: Clay Canyon, Fairfield, Oquirrh Mts, Utah Co., Utah, USA. It also occurs as a late-stage mineral in highly oxidized phosphates in granitic pegmatites, as at the Tip Top mine (Tip Top pegmatite), Fourmile, near Custer, Custer Co., SD, USA, where it is associated with triphylite, tiptopite, pahasapaite, roscherite, hurlbutite, englishite, whitlockite, fransoletite, and todorokite. Other notable localities for montgomeryite include: Etta mine, Keystone, Pennington Co., South Dakota, USA; Bendada, Guarda, Portugal; Huhnerkobel, Bavaria, Germany; Bruguers, Catalonia, Spain; Taldyk, Qaratau Plateau, Kazakhstan; and Iron Monarch quarry, Iron Knob, South Australia.

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