Original paper

Hingganite-(Y) from the Zomba-Malosa complex, Malawi

Petersen, O. V.; Leonardsen, E. S.

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Neues Jahrbuch für Mineralogie - Monatshefte Jg. 1994 Heft 4 (1994), p. 185 - 192

24 references

published: Apr 8, 1994

DOI: 10.1127/njmm/1994/1994/185

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Abstract

The rare mineral hingganite- (Y) has been identified in agpaitic granite pegmatites in alkaline granites from the northern-Malosa-part of the Zomba-Malosa complex of the Chilwa alkaline province, Malawi. The paragenesis closely resembles the paragenesis of the pegmatite at Narssârssuk, South Greenland and contains potassium feldspar, albite, aegirine, arfvedsonite, riebeckite var. crocidolite, quartz, zircon, pyrochlore, epididymite, eudidymite, polylithionite, mangan - neptunite, parisite-(Ce), bastnäsite-(Ce), fergusonite-(Y), hematite, goethite, ilmenite, rutile (?) and hingganite-(Y). The hingganite-(Y) forms 1 mm individual crystals and fan- and sheafshaped aggregates, up to almost 2 mm. The crystals are pale bluish and transparent with a vitreous lustre. The larger crystals are dominated by {110} and {111} with only minor faces of {001}; simpler crystals show only {110} and {001}. Optically the Malawi hingganite - (Y) is biaxial positive with 2Vɑ meas. = 117±3°, nɑ = 1.7446±0.0005, nß = 1.7518±0.0005 and nγ = 1.7729±0.0005, 2Vɑ calc. = 119±3°;ß = b, 𝞬 𝝠 c = 13° in the acute angle ß. The unit cell parameters of the hingganite-(Y) from Malawi are: a = 4.733±0.003, b = 7.606±0.003, c=9.895±0.006 Å and ß = 90.347±0.001°. Both the optical properties and the unit cell parameters correspond well with those presented for hingganite-(Y) from the type locality - Greater Khingan area, China. The chemical composition of the Malawi hingganite-(Y) has been established by electron microprobe and by optical emission spectrographic analyses for Be. The chemical composition of the hingganite-(Y) from Malawi corresponds well with that presented for hingganite -(Y) from Japan; compared to hingganite-(Y) from the type locality the Malawi hingganite-(Y) is very much enriched in Y.

Keywords

Hingganite-(Y) • Zomba-Malosa complex • Malawi