New Mexico Mineral Symposium — Abstracts

The term "telluride vein" is descriptive with respect to the constituents of the minerals within the vein. Most, if not all, telluride veins are also sulfide veins, for they contain many of the base metal sulfide minerals, such as sphalerite, pyrite, galena, and markasite. The relationship of these minerals seems to depend on the preference of the metal anion to associate with either sulfur or tellurium. Because gold does not associate with sulfur, telluride minerals, i.e. calaverite, sylvanite, krennerite, and petzite, in the assemblage give the vein its unique and distinct identification—"telluride vein."

Nearly all the base metals have their telluride counterpart, i.e. Pb—galena—altaite, Fe—pyrite-frohbergite, Ag—argentite—hessite, Cu—chalcopyrite—rickardite, etc. There are no known Zn tellurides, and some metals do not form tellurides, such as cobalt, tin, molybdenum, etc.

Telluride veins form a very conspicuous gossan in the areas where the vein is protected from erosion. Any vein that has abundant pyrite will form the iron hat (gossan). It is in the gossan that we find the rare "rusty gold" and many of the secondary tellurium minerals, such as tellurates and tellurites. Rusty gold forms when ground water leaches away the tellurium from sylvanite leaving the gold molecules in place. These pseudomorphs of gold after sylvanite are the rarest form of gold there is. Few collections have samples of this rare mineral.

The telluride veins of the Gold Hill district in Colorado were given the term "pocket veins" because the miners did not understand the mode of occurrence of the rich cymoid structures that occur along the strike of the vein. They would mine through the structure and wonder why the values diminished on the other side, not realizing that they had to follow the cymoid structure to stay in paying ore. Many discoveries and prospects were abandoned because the ore values diminished with progress along a tunnel, whereas, if they had followed the cymoid structure they would have been in good ore for many hundreds of feet.

Telluride veins are most often narrow fissures, and the size of the pay streak that carries the values is what determines the richness of the mines. Due to earth shifts, the veins of the Gold Hill district opened many times, causing a new implantation of minerals in many quartz stringers that may or may not be blessed with telluride values.