Wolff sent the specimens, labeled as "dumortierite
," to the firm of Gebruder Bank in Idar-Oberstein, Germany for identification.
Schneider and Seeger (1992b) report bright deep blue dumortierite
from a pegmatite on the farm Etemba 135, close to the northern boundary of the Erongo Mountains.
Associated minerals are: quartz, dumortierite
, kaolinite and rutile.
Associated minerals are: quartz, microcline, sillimanite, surinamite, musgravite, "garnet," biotite, "apatite," rutile, dumortierite
Wolff"; the stones were labeled as possibly iolite or dumortierite
. Hermann Bank and Professor Waldemar Berdesinski of the University of Heidelberg identified them as zoisite.