Xenotime from Morrua, Mozambique

Abstract

Xenotime, found as well formed crystals in a heavy mineral concentrate from the Morrua pegmatite mine in Mozambique, was studied. The mineral occurs in the sample in two generations, clearly distinguishable from each other. The first generation crystals are turbid with varying color and are dominated by the faces (110) and (001). The second generation crystals are yellow, entirely transparent and exhibit the sequence (100)-(301)-(101)-(001) in the development of the crystal faces. The mineral is highly yttrian with an atomic ratio yttrium/lanthanides = 78:22 and, in the relative abundance of the lanthanides, shows a strongly pronounced maximum of gadolinium. X-ray and optical data and density are given.

Dysprosian Xenotime-(Y) From the Annie Claim #3 Granitic Pegmatite, Southeastern Manitoba, Canada: Evidence of the Tetrad Effect?

“…Increased quantities of individual HREEs, such as those in xenotime-(Yb) (Buck et al 1999), are exceptional, although moderate enrichment in Yb, Dy and Gd has been occasionally noticed (Vlasov 1966, Sahama et al 1973, Franz et al 1996. Here we report on the occurrence of xenotime-(Y) with the highest content of Dy ever reported in this mineral, from a lepidolite-subtype granitic pegmatite in Manitoba.…”

“…A strong positive Gd anomaly was recorded by Sahama et al (1973) in xenotime-(Y) from the Morrua pegmatite, Mozambique, but only in terms of relative abundance compared to other REE; quantitative data were not obtained. Otherwise, moderately Gd-enriched xenotime was encountered only by Franz et al (1996) in metapelitic lithologies (Table 1, compositions 7 and 8, Fig.…”

Growth of a beryl single crystal–history of the development and the genetic medium

“…The results of this work show how the examination of samples by X-ray topography coupled with other research techniques, such as optical microscopy and electron microprobe, for instance, provides the desired correlations, even when geological and petrographic data concerning the origin of the sample are totally missing. The investigated sample was kindly provided by Professor T. G. Sahama (1966). Unfortunately, its origin (geological and petrographic context of the pr~l~vement) was not given.…”

Th.G. Sahama's (1910-1983) volcanological and mineralogical studies in Africa: Part ii. Minerals of granitic pegmatites and other mineral occurrences of eastern and southern Africa

“…presented a mineralogical description of bismutite, a bismuth carbonate, occurring as "bismuth ocher" together with minor amounts of metallic bismuth in some Zambezian pegmatites. v. Knorring et al (1973) described two bismuth vanadate minerals from the Mutala pegmatite with the formula BiVO 4 : an orthorhombic pucherite and an unknown (new) orthorhombic yellow mineral for which they presented crystallographic data including indexed scanning electron micrographs of crystals, unit cell dimensions and chemical composition. The data matched the properties of a synt-hetic monoclinic bismuth vanadate, and v. Knorring et al (1973a) described the mineral simply as "natural monoclinic bismuth vanadate".…”