KKDucH.] GEOLOGY MINEEALOGICAL NOTES. 353 



Some distance to the southwest of the Eed Cloud we find the Central, 

 Seven-Thirty, and Americus, located contact to a long dike of porphyry 

 and the surrounding gi-anite. In a light-gray microcrystalliue paste we 

 find embedded numerous small crystals of black mica, crystals of a prob- 

 ably triclinic feldspar, and small, irregular particles of white quartz. 



Of all the veins located on this dike, the main one is chalcopyrite and 

 pyrite, with the usual accessories; sphalerite and galenite occurring 

 rarely. In none of the specimens that reached me could I find any tel- 

 lurets, although their analogous mode of occurrence might lead to some 

 •expectation of their presence. 



In various parts of the world, compounds of tellurium with other 

 metals have been found, so that the first attempt at recognizing analo- 

 gous minerals from the Gold Hill region was to identify them with those 

 already described. It seems to me that the tellurets of the region under 

 consideration show a greater variety of composition than those of other 

 localities. For entering into combination with other elements, the facil- 

 ities must have been great ; we have one compound, that of tellurium 

 and iron, which, although not occurring pure, enters into the formula 

 of the mineral. During the coming field-season, I expect to obtain a 

 satisfactory supply of material, in order to give a complete synopsis of 

 the mineral-occurrences of the Gold Hill locality. 



Two minerals were found, occurring both at the Eed Cloud and Cold 

 Spring lodes, that could not strictly be parallelized with any known 

 species, and I have reserved the right of distinguishing them by a sepa- 

 rate name, if subsequent examinations of more abundant and purer 

 material will warrant it. 



Xo. 1. 



Isometric, imperfect crystals observed. Cleavage cubical, good. 

 Mostly found in thin threads, or in small, irregular, foliated masses. 



Hardness, 2 to 2.5. Specific gravity, 8.5253. Luster metallic, splendent. 

 Color bright silver-gray to steel-gray ; pale bright-yellow when exposed 

 to atmospheric influences a short time. Streak metallic, gray to silvery. 

 Opaque ; brittle ; partly malleable and sectile. 



On account of the small quantities that could be spared for analysis, 

 the tellurium was not determined but calculated ; the result of careful 

 qualitative examinations having revealed no trace of any other elements 

 than those found and given below. 



By analysis the following constituents were obtained: 



Pb, Fe, Ag, Au, Te by diff., 

 53.19 5.05 0.31 trace 41.45 =100.00 



Calculating the simi3le tellurets for each one of these constituents, 

 we find there are required for — 



53.19 Pb, 5.05 Fe, 0.31 Ag, 



32.90 11.55 0.19 = 44.64 tellurium. 



It is probable that Slight replacements may account for the smaller 

 quantity of tellurium found. 

 The percentage of constituents found leads to the formula — 



3 Pb Te + Fe Te 



a very minute portion of lead having been replaced by silver. During 

 the examination, great pains were taken to procure the mineral as pure as 



23 G s 



