Iron-rich chrysoberyl from Kalanga Hill, Muyombe District, north-eastern Zambia
Žá ček, Vladimí r; Vrá na, Stanislav
published: Dec 9, 2002
Pegmatite with abundant chrysoberyl occurs at Muyombe in north-eastern Zambia near the Zambia/Malawi border. The pegmatite is composed of quartz, feldspar, chrysoberyl, beryl, muscovite, accessory Nb-Ta oxides and zircon. It cuts HT/LP cordierite - garnet - sillimanite - biotite - spinel granulite of the Ubendian Crystalline Complex. Chrysoberyl is exceptionally rich in iron (3.16-6.25, mean 5.1 wt.% Fe2O3) and zoned with rimward decrease of Fe. The most prominent substitution Fe3+ Al-1 corresponds to the empirical formula ranging from Be(Al1.94Fe0.05)O4 to Be(Al1.90Fe0.10)O4. Minor TiO2 (up to 0.6 wt.%) and MgO (up to 0.3 wt.%) are also locally present. Lattice parameters calculated from powder diffraction data are: a = 4.4326(07), b = 9.4256(18), c = 5.4893(10) (Å), V = 229.34(07) (Å3). The origin of chrysoberyl is discussed.