Also see
http://www.mindat.org/min-1775.html gumucionite
"Julio F. Gumucio was chief engineer at Llallagua, working for "tin baron" Simon Patino. In his old age he managed the railroad yard at the nearby smelter town of Machacamarca. His mineral collection was the finest ever assembled by a native Bolivian. The collection went to the Banco Minero after his death, then into storage for several years after the death of the bank. The remnants are now on display to the public in the Casa de la Moneda"
HERZENBERG, R. (1932) Gumucionitte, una nueva variedad arsenical de blenda. Rev. Mineral., Geol. Mineral., Soc. Argent. Mineral. Geol., 4, 65-66.
HERZENBERG, R. (1933) Gumucionit, eine neue arsenhaltige Varietat der Schalenblende. Zentralblatt fur Mineralogie, A, 1933, 77-78.