Wyllieite and rosemaryite in the pegmatite of Buranga, Rwanda
Wyllieite et rosemaryite dans la pegmatite de Buranga, Rwanda
European Journal of Mineralogy (June 1995) 7 (3): 567-575
These two phosphates are noted for the first time from the Buranga pegmatite, having been identified in both cases by EPMA, wet chemical analysis and XRD. The wyllieite has a 11.967, b 12.462, c 6.409 Aa, beta 114 degrees 38'; alpha 1.685, beta 1.688, Gamma 1.692, 2V<F128MV>g<F255D> 90 degrees ; alpha colourless, beta = Gamma bluish green. It occurs as bottle-green globular grains within trolleite masses, in close association with scorzalite; its Fe/(Fe + Mn) is 0.41-0.47. The rosemaryite has a 11.977, b 12.388, c 6.320 Aa, beta 114 degrees 27'; alpha 1.723, beta 1.742, Gamma 1.758, 2V<F128MV>a<F255D> 80 degrees ; alpha = beta weak brownish yellow, Gamma weak greenish yellow. It also occurs within the trolleite masses and at the contact of allaudite-Na<P6M><$B0><P255D> with montebrasite; its Fe/(Fe + Mn) value is 0.44-0.46 (or 0.52 when with montebrasite). It is suggested that in the trolleite association rosemaryite is derived from wyllieite by oxidation.