BEUSITA EN LA PEGMATITA SAN JOSÉ Nº 2, CÓRDOBA, ARGENTINA

COLOMBO, FERNANDO; GAY, HEBE DINA; SFRAGULLA, JORGE; LIRA, RAÚL

Buenos Aires

Congreso; 6º Congreso de Mineralogía y Metalogenia; 2002

Departamento de Ciencias Geológicas (UBA).

Beusite, (Mn,Fe,Ca,Mg)3(PO4)2, has been found in the San José Nº 2 pegmatite (32º 09´ 43,8´´ S, 64º 56´ 17,4´´ W), Calamuchita department, Córdoba province (Argentina). It is a zoned body some 200 m long and between 15 and 30 m wide. Border and wall zones might be present but have not been observed. The pegmatite has an outer intermediate zone (plagioclase + quartz + muscovite) and an inner intermediate zone (quartz + plagioclase + muscovite or quartz + K-feldspar + muscovite). Accesory species include garnet, columbite-group minerals, gahnite and beryl. The core is composed of massive quartz. A single piece of beusite was found in the dump. It is massive, dark to medium brown and has a black rind of alteration products. Luster ranges from glassy on cleavage surfaces to greasy on fractures. Dcalc = 3.70 gr.cm-3. Microprobe analyses (wavelenght dispersive mode) are as follows (weight %, average of 3 points): P2O5 39.42, MnO 29.39, FeO 22.57, CaO 5.73, MgO 0.30, SiO2 0.01, F 0.00, Cl 0.00, total 97.42 wt. %. Indices of refraction are: a = 1.704(3), b = 1.708(3), g = 1.722 (3); 2Vcalc = 28.3º. Dispersion r > v, strong; no pleochroism, X = Y = Z = very light brown. Cell parameters are a = 8.757(2) Å, b = 11.830(2) Å, c = 6.1603(5) Å, b = 99.81(1)º. Cell volume is 628.8(4) Å3. The diffraction lines match those of card 36-0401 of the JCPDS (1997).