Abstract

The rare hydrous scandium phosphate, kolbeckite, [Sc(PO4).2H2O], has been recognized for the first time from the Hagendorf-Pleystein pegmatite province. The mineral was formed by the alteration of quartz-rich relict cores of pegmatites containing rutile, ilmenite, columbite, pyrochlore, wolframite, monazite and apatite. The alteration process involved acidic meteoric water and was not related to low-temperature hydrothermal fluids. Scandium and phosphorous for the formation of the kolbeckite were provided by the decomposition of the primary oxides and phosphates, respectively. Hydrous Sc phosphates are considered to form only during advanced stages of weathering in Al- and Fe-poor environments. In Al- and Fe-rich environments Sc is scavenged from solution as a trace component of Al- and Fe phosphates. A special type of leucoxene containing Fe, Al and P was formed during the process of formation of kolbeckite. In the absence of phosphate anions, Sc is removed in solution and ‘normal’ leucoxene is formed.

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