gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1992.056.382.07 Mineralogy and Petrology A New Occurrence of Vesigniéite from the Gorob-Hope Copper Deposit, Namibia Schneider G. I. C. Geological Survey of Namibia P.O. Box 2168 Windhoek 9000, Namibia Lauenstein H. -J. Tsumeb Corporation P.O. Box 40 Tsumeb 9000, Namibia 3 1992 56 382 67 69 19 10 1989 20 7 1991 Copyright © 1992, The Mineralogical Society 1992 Abstract

An iron-rich vesigniéite, [Ba(Cu,Fe)3(VO4)2(OH)2] with Cu : Fe near 4 : 1, was identified in samples from the submarine-exhalative Gorob-Hope copper deposit, Namibia. The olive-colour mineral occurs as mammillary encrustations and vein fillings in the gossan zone of this deposit; it often has a brownish oxidation coating. The main X-ray lines are 3.21 Å (100) [204, 113], 2.72 Å (63) [313, 002] and 2.94 Å (61) [020, 311]. The cell parameters are a = 10.236, b = 5.905, c = 14.253 Å and ß = 103.71°. The formation of vesigniéite took place during the alteration of the ore under strongly alkaline and slightly reducing to oxidizing conditions. While copper and barium were derived from the submarine exhalative mineralisation, vanadium was leached from the countryrock, a micea schist.

 Keywords vesigniéite vanadate Gorob-Hope deposit Namibia