Introduction. In Vol. Il of the monograph: "Die Mineralien der südnorwegischen Granitpegmatitgange" I have, on page 144, made some remarks about the dubious mineral "høgtveitite" announced in a mineral index from the mineral dealer Dr. L. Eger, Vienna. I presumed that høgtveitite could be identified with a dark nutbrown mineral occurring together with fergusonite from granite pegmatite at the farm Høgtveit in Evje, Setesdalen. On the base of well-developed tetragonal crystals of zircone type sitting on the top of one of the specimens from Høgtveit and looking to be the termination of the mineral mass against the surrounding feldspar, I determined the mineral erroneously as alvite (altered variety of zircone quite near cyrtolite). Later V. M. Goldschmidt and L. Thomassen undertook a systematic X-ray-spectrographic investigation of all known occurrences of the mineral alvite from Norway for determination of the geochemical distribution of the element hafnium. For this purpose mr. Thomassen at my request prepared an X-ray-spectrogram of the presumed alvite from Høgtveit with the result that the X-rayspectrogram of this mineral only showed lines of the rare earths of the yttriumgroup but no traces of the lines of zirconium and hafnium. According to this the mineral most probably was a silicate chiefly of the rare earths of the yttriumgroup and in composition probably analogous to the mineral thalenite (Benedicks). At my request miss Helga Hougen undertook an analysis of the mineral from Høgtveit, mentioned later on in this paper, which showed that the mineral chiefly is a silicate of yttria but that it differs from the Swedish thalenite through higher contents of Al2O3 and water. A new and very carefull investigation of the specimen from Høgtveit with the tetragonal crystals showed that these crystals were independent crystals of veritable a/vite grown in the dark brown silicate of yttria and of nearly the same colour.
Remarks on thalenite from some new occurences in Southern Norway
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