Columbite–Tantalite from Northern Scandinavia (Kaustinen, Kolmozero) Pegmatites: An Optical and Spectroscopic Properties

Abstract

LCT (lithium–cesium–tantalum) pegmatites from the Kaustinen and Kolmozero regions contain columbite–tantalite mineralization, which has been presented in this study. Crystal structure, Raman microscopy, and optical property analyses of these minerals were performed. As a result of the structural studies and micro-area analyses, it was determined that these minerals in the pegmatites in question constitute a solid solution with numerous Mn-Fe and Nb-Ta substitutions within a single crystal. The ratio between Mn-Fe and Nb-Ta can change from crystal to crystal, which makes it impossible to find precise stechiometry between these ions. The crystallization conditions of these minerals were also determined by studying the associations of other rock-forming minerals and accessory minerals in the discussed rocks.

The Optical and Spectroscopic Properties of Fuchsite, Spodumene, and Lepidolite from Northern Scandinavia (Kautokeino, Kaustinen, Kolmozero)

“…In addition, opaque minerals were found in the exanimated rocks. In the Kolmozero pegmatite, columbite ((Fe,Mn)Nb 2 O 6 ) forms euhedral crystals, usually close to spodumene, quartz, and plagioclase [2]. Along with columbite, tantalite is visible.…”

“…In northern Scandinavia, pegmatite veins containing rare lithium and schists with chromium minerals are found in the regions of northern Norway [1], Finland [2], and the Kola Peninsula in Russia [3], among rocks constituting the cratonic basement of the Northern Fennoscandia [4]. These rocks contain minerals such as mica (lepidolite, fuchsite, muscovite) and pyroxene (spodumene), which co-occur with quartz, plagioclase, orthoclase, and several ore minerals: oxides (e.g., columbite, tantalite, cassiterite, sillenite, clarkeite) and sulfides (pyrite, chalcopyrite).…”

“…1 1/2 + X,1-Y,+Z;2 3/2-X,1/2-Y,1/2-Z; 3 1/2-X,1/2-Y,1/2-Z; 4 1-X,-1/2 + Y,1/2-Z; 5 -1/2 + X,-1/2 + Y,-1/2 + Z; 6 +X,1/2-Y,-1/2 + Z;7 1/2-X,+Y,-Z; 8 -1/2 + X,1/2 + Y,-1/2 + Z.…”