MANGANGORDONITE, A NEW PHOSPHATE MINERAL FROM KINGS MOUNTAIN, NORTH-CAROLINA AND NEWRY, MAINE, USA

Mangangordonite is a new phosphate mineral from the Foote Mineral company spodumene mine, Kings Mountain, North Carolina, and the Dunton Gem mine, Newry, Maine, USA. Electron microprobe analyses of Kings Mountain material gave MgO 0.35, MnO 10.79, FeO 3.37 (total Fe), Al2O3 22.03, P2O5 29.46, normalized to 66%, H2O; by stoichiometry 34.14. Based on structure analysis and analogy with gordonite, the ideal formula is MnAl2(PO4)2(OH)2(H2O)6.2H2O. The mineral forms mm-size euhedral crystals within vugs in spodumene-microcline-quartz pegmatite (Kings Mountain) or in pegmatite composed of pale blue tourmaline, siderite, quartz, and muscovite (Newry). Mangangordonite from Kings Mountain is transparent, colorless to faintly yellow, with a vitreous lustre. It is nonfluorescent. The streak is white, hardness is about 3, S.G. 2.36(3), calc. 2.319. Mangangordonite is brittle, with perfect {010} cleavage. Optically, it is biaxial +, alpha 1.556(1), beta 1.561(2), gamma 1.571(2), 2V 70-degrees, calc. 71-degrees, r < v distinct, Z near c, (010):OAP approximately -45-degrees. It is triclinic P1BAR, a 5.257(3), b 10.363(4), c 7.040(3) angstrom, alpha 105.44(3)-degrees, beta 113.07(3)-degrees, gamma 78.69(4)-degrees, V 340.7(3) angstrom 3, Z = 1. The strongest X-ray diffraction lines are (d, I, h k l) 9.96, 6, (010); 6.39, 8, (001); 4.77, 10, (111); 3.18, 7, (002); 2.86, 5, (112); 2.59, 4, (032). Crystals are nearly equant to tabular on {010}, slightly elongated along [001]. Forms present are {010}, {100}, {001}, {11BAR0}, {01BAR1}. Twinning was not observed.