Watermelon tourmaline from the Paprok mine (Nuristan, Afghanistan)
Natkaniec-Nowak, Lucyna; Dumańska-Słowik, Magdalena; Ertl, Andreas
published: Aug 1, 2009
ArtNo. ESP154018602004, Price: 29.00 €
The “watermelon” tourmaline from the Paprok mine (Nuristan, Afghanistan) shows different tourmaline components. Four zones differ widely what is reflected by different chemistry and various colours (pink core and green rim). All zones show a relatively low Mn content (∼0.05 apfu) but different Fe contents. While Fe is in the (pink) core at the detection limit, it increases significantly in the outer (green coloured) zones. In the core (zone I) “fluor-elbaite” could be identified for the first time for the Nuristan region. Tourmaline compositions of this zone show an elbaitic component of ∼55 mol%, ∼30 mol% rossmanite- and ∼15 mol% liddicoatite-component. Zone II shows an increasing schörl- and rossmanite-component (up to 40 mol%), while the liddicoatite- and elbaite-components are decreasing. The intermediate zone III shows the highest schörl-component of all zones (up to ∼11 mol%), while the elbaite-component is decreasing. In the rim (zone IV) the schörl-component decreases to ∼6 mol%, while simultaneously the elbaite-component increases. Our investigation shows that during tourmaline crystallization only the amounts of Fe and Li, which were available for the tourmaline crystallisation, have changed to a significant degree. We believe that at beginning of the crystallisation of the Fe-bearing zones the formation of Fe-rich tourmalines (schörl, foitite) in this pegmatite was in a final stage and therefore in this pegmatitic system Fe increasingly was available. The Mn/(Mn+Fe) ration ranges from ∼0.10 to ∼1.00. The presence of different mineral inclusions such as stannite and Ca carbonates point to a hydrothermal origin of this tourmaline.