Tourmaline from Věžná I pegmatite; an indicator of externalcontamination and internal fractionation

Minerals of the tourmaline group are chemically very variable and therefore are good indicators of the degree of fractionation and pegmatite contamination. A typical example is the Věžna I locality. There were 6 types of tourmalines found in different zones of pegmatite. In the outer zones, Mg rich dravite predominates, replacing by schorl and foitite, and in the most fractionated parts by Mn and Li rich elbait and fluor-elbait. Tourmalines from more fractionated zones are secondary contaminated with Mg from the host serpentinite.