SPECIES FROM THE PHOSCORITE–CARBONATITE UNIT, KOVDOR COMPLEX,

Gladiusite, ideally Fe3+2(Fe2+,Mg)4(PO4)(OH)11(H2O), monoclinic, a 16.959(2), b 11.650(3), c 6.266(6) Å, 90.00(5)°, V 1238(1) Å3, space group P21/n, Z = 4, is a new mineral species from hydrothermal assemblages associated with the phoscorite– carbonatite unit of the Kovdor alkaline-ultramafic complex, Kola Peninsula, Russia. It occurs in vugs within veins of mineralized dolomite carbonatite. Associated minerals are dolomite, pyrochlore, several generations of magnetite, pyrite, rutile, a ternovite-like phase, catapleiite, bobierrite, rimkorolgite, juonniite, strontiowhitlockite, collinsite (including a Sr-rich variety) and chlorite. Gladiusite occurs as acicular aggregates and as free-standing radial clusters (<2 mm in diameter) of arrow-headed crystals. Acicular crystals vary from 0.5 to 6–7 m thick and from 10 to 500 m long. Gladiusite is dark green, almost black, with an olive-green streak, opaque in aggregates and translucent in thin crystals; it has a vitreous luster, and does not fluoresce under long- or short-wave ultraviolet light. It has a Mohs hardness of 4–4, and is brittle with an irregular fracture; cleavage and parting were not observed. The measured and calculated densities are 3.11(2) and 3.10(4) g/cm3, respectively. Gladiusite is biaxial negative and strongly pleochroic, 1.722(2), 1.730(2), 1.737(2), 2Vcalc. = 78.3°. The strongest reflections in the X-ray powder-diffraction pattern [d in Å(I)(hkl)] are: 9.61(53)(110), 6.87(77)(210), 5.83(89)(020), 4.805(100)(220), 3.787(62)(130), 3.533(84)(230), and 2.868(66)(140). Electron-microprobe analysis and Mössbauer spectroscopy gave (wt.%) FeO 25.00, Fe2O