Primary Native Silver Ores at Batopilas, Mexico, and Bullard's Peak, New Mexico

Many of the silver deposits on which there is seemingly general agreement as to their hypogene (primary) origin, and particularly those deposits in which native silver is a fairly common constituent, show a characteristic association of nickel and cobalt arsenides with native silver or other silver minerals. In view of the generally recognized hypogene origin of the nickel and cobalt arsenides this association has been used as one of the criteria for the primary origin of native silver. Such an association has been observed in a number of localities and described by various writers. It is one of the striking features of the silver deposits in the Erzgebirge of Europe. A similar association in the mines of the Cobalt district of Ontario is so well known that further mention is not necessary. In addition to these two best known of the districts where this association is common, Bastin1 has also described silver deposits near Wickenburg, Arizona, where the same association is found and where he believes much of the native silver as well as other silver minerals are due to hypogene mineralization. More recently the deposits of the Great Bear Lake district have been studied by Kidd2 where a similar association is noted. Piepoli3 has described the ores of Sarrabus, Sardinia, where cobalt and nickel arsenides are associated with native silver and pyrargyrite. The silver minerals at this locality are also considered to be of primary origin. At Sabinal, in Chihuahua, Mexico,4 native silver and other silver minerals are intimately intergrown and associated with similar arsenides and with galena, sphalerite, chalcopyrite and pyrite.