Genesis of yellow manganese-rich elbaite from the Canary mining area,Lundazi, Zambia |
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| Authors: | Brendan M Laurs William B Simmons Alexander U Falster Björn Anckar |
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| Institution: | 1. Gemological Institute of America (GIA), The Robert Mouawad Campus, 5345 Armada Drive, Carlsbad, CA 92008, USA;2. Department of Earth and Environmental Sciences, University of New Orleans, GP Building 1065, 2000 Lakeshore Drive, New Orleans, LA 70148, USA;3. GemGeo Consulting, Driveslattvagen 102, Alingsas, SE-44191, Sweden |
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| Abstract: | The most important source of yellow gem elbaite is the Canary mining area in the Lundazi District of eastern Zambia. The tourmaline has been mined since 1983 from both pegmatite and eluvial/alluvial deposits, in colors typically ranging from yellow-green to yellow to orange and brown; much of the orange-to-brown material is heated to attain a ‘golden’ or ‘canary’ yellow color. The elbaite is Mn-rich (up to 9.18 wt% MnO documented in the literature) and contains small amounts of Ti and little or no Fe. The distinctive composition of this tourmaline is probably the result of the early crystallization of abundant schorl from an unusual B-rich, Li-poor pegmatite melt, which depleted Fe while conserving Mn until the late-stage crystallization of gem pockets. The simple mineralogy of the pegmatite consists of feldspars, quartz, and tourmaline; the lack of micas, phosphates, or Li minerals, and the presence of very little garnet, allowed Mn to fractionate to high levels during pegmatite crystallization. The presence of abundant gem tourmaline in a Li-poor pegmatite is highly unusual. |
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