SOUTH AMERICAN LOCALITIES. 19 



traces of antimony. The first step is an oxidation of stibnite to stibiconite, 

 accompanied by a more or less complete impregnation witli black, amorphous 

 metacinnabarite. The transformation of the whole mass to cinnabar follows. 

 The change from black to red sulphide is considered as due to the probable 

 solubility of mercuric sulphide in calcium sulphide. Quartz and gypsum 

 are the gangue minerals.^ 



At Clnlapa also, near Tixtla, cinnabar occurs in a well defined vein 

 in metamorphic slate. Quartz and iron oxides constitute the gangue, and 

 the vein matter incloses fragments of country rock. In places the quartz 

 is stained with copper. Cinnabar impregnates the entire width of the vein. 

 At San Onofre mercurial ores occur under conditions similar to those 

 at Guadalcazar; near San Felipe are veins of cinnabar in porphyry: near 

 Guanajuato deposits of cinnabar and mercuric iodide occur in Tertiary 

 clays and conglomerates ; at Loma de Encinal veins of cinnabar exist in 

 decomposed porphyry; and rich mercurial deposits are said to occur at 

 Maltrata. In 1876 Mr. Geo. T. Walker, reporting in manuscript on the 

 Guanacevl district, in the State of Durango, calls attention to the fact that, 

 in the La Colcrada silver mine, ores containing cinnabar occur close to the 

 hanging wall of the vein. This occurrence has a parallel in this country 

 near Belmont, Nev. 



Guatemala. — Accordiug to Noggeratli, a specimen of cinnabar from Gua- 

 temala, accompanied by barite, exists in Berlin. I have met with no other 

 mention of quicksilver ores in Central America. 



SOUTH AMERICA. 



Colombia. — ]\Ir. R. R. Hawkins, of my staff", found native quicksilver 

 disseminated in globules in a clay soil near the town of Cruces, on the Isth- 

 mus of Panama. He also found float cinnabar near the Magdalena river, 

 in the State of Tolima. " Near Choco," probably the bay o-f that name, 

 " gold amalgam and platinum are found together."- Humboldt mentions 

 cinnabar as occurring in the province of Antioipiia, in the valley of the 

 Santa Rosa, to the east of the river Guaca, and also between the towns, 

 Ibague and Carthago. 



' Sitznngsber. k. bayer. Akad. Wiss., Municb, July 3, 187.5. 

 • Niiggerath, loc. cit. 



