Foorumite

Foorumite is a rare phosphate mineral described from hydrothermal veins. It crystallizes in the monoclinic system and forms slender tabular to prismatic crystals up to about 2 cm. The color ranges from pale brown to olive-green, and it has a vitreous to resinous luster. On the Mohs scale, foorumite is about 5 in hardness. It commonly occurs with quartz, calcite, and fluorite in hydrothermal and skarn assemblages.

Chemically, foorumite is a calcium- and iron-rich phosphate with magnesium, sodium, and aluminum as admixtures. A simplified idealized formula is (Ca,Na)(Fe,Mg)3(PO4)2(OH)2, with variable hydration. It occurs in solid solutions with trace aluminum and rare earth elements. The crystal structure consists of phosphate groups connected by mixed-metal cation layers, allowing partial substitution by different ions.

Occurrence and locality: Type material was discovered in the Fooru district; later reports describe foorumite in several hydrothermal environments worldwide, often in carbonate rocks affected by skarnization or near contact metamorphic zones. It is typically associated with quartz, calcite, fluorite, and dolomite.

Etymology and taxonomy: The mineral was named foorumite after the type locality; the name was approved by the International Mineralogical Association in 1999. It is of interest primarily to mineral collectors and researchers studying phosphate minerals and hydrothermal processes. The discovery contributes to understanding compositional flexibility in phosphate solid solutions and the geochemical conditions that stabilize such minerals.