Hejtmanite, a manganese-dominant analogue of bafertisite, a new mineral

Hetjmanite forms prismatic or platy crystals <= 1 mm long enclosed in manganoan arfvedsonite veins in foliated alkali granite and syenite at Mbolwe Hill, Mkushi River area, Central Province, Zambia. EPMA gave SiO (sub 2) 23.52, TiO (sub 2) 13.27, Nb (sub 2) O (sub 5) 1.4, Al (sub 2) O (sub 3) 0.37, FeO (sub tot) 11.29, MnO 14.12, MgO 0.13, BaO 30.2, Na (sub 2) O 0.06, K (sub 2) O 0.30, F 3.3, Cl < 0.1, H (sub 2) O 1.86 = 98.43, leading to the idealized formula Ba(Mn,Fe) (sub 2) TiO(Si (sub 2) O (sub 7) )(OH,F) (sub 2) . It is brownish yellow to golden yellow, transparent and pleochroic with alpha (light green-yellow) 1.814, beta (dark golden yellow) 1.846, gamma (light yellow) 1.867, 2V (sub alpha) 76.4 degrees, gamma:a 15.9 degrees ; perfect cleavage 100. Indexed XRD powder data are tabulated; strongest lines 2.726(100), 5.472(32), 3.241 + 3.215(21), 3.455(17), 2.180(16) Angstrom ; a 11.748, b 13.768, c 10.698 Angstrom, beta 112.27 degrees ; diffraction symbol A*/*; isotypic with bafertisite; D 4.016 g/cm (super 3) ; the IR absorption spectrum is presented. The name is for B. Hejtman, Emeritus Professor of Petrology, Charles University, Prague, and it is proposed that it be used for the Mn (super 2+) > Fe (super 2+) members of the solid solution with bafertisite. Analyses are also reported for the host manganoan (MnO approx 5%) arfvedsonite.