BILLIMAN.] 



TELLURIDE ORES. 689 



line of contact of the walls of the dike, in a quartz gangne, associated 

 chiefly with pyrite in small, brilliant, highly-modified crystals, and rarely 

 with chalcopyrite and sphalerite. Professor Hill speaksVoc. cit) of lead ; 

 but I have found no salts of this metal in the specimens received. The 

 quartz is chiefly hornstone and uncrystalline quartz, and, on the side of 

 the country-rock, it is mixed with feldspar. Native gold is not visible 

 in any of the specimens I have seen of this ore from below the surface; 

 but where the surface is weathered, it exhibits free gold, arisiug from 

 the decomposition of the tellurets. 



On the sides of the dike, the line of division is clearly defined, but not 

 so on the side adjacent to the metamorphic rocks, it blending on this 

 side with the granitic materials. The thickness of the veins varies from 

 four or six feet to a few inches, but the rich tellurium- ores form a com- 

 paratively narrow seam near the center of the vein. The Eed Cloud 

 mine, which is found on the under side of the dike, has been explored to 

 a depth of about 70 feet. The Cold Spring mine is explored on the 

 upper side of the dike. The tellurium- ores are not found in the body of 

 the dike, but have (owing probably to the long-continued high tempera- 

 ture of the dike) found lodgment in the granite outside of the walls, and 

 not in immediate contact with them. 



The species at the Eed Cloud mine are native tellurium sylvauite and 

 hessite, (which has been called petzite.) The simplicity of the mineral- 

 ogy of this locality is in strong contrast with what is found in the tel- 

 lurium-veins of Transylvania, which are mentioned more particularly 

 farther on. 



Native tellurium. — The occurrence of this rare species in the United 

 States, in California, was mentioned by Dr. Genth, with a query, in his 

 Contributions to Mineralogy, No. vii, (American Journal of Science, II, 

 xlv, 313.) Its existence in the Eed Cloud mine is unequivocal. It 

 was simultaneously, yet independently, detected by Dr. Endlich and 

 myself in a small specimen from the collection made at the mine last 

 summer, and now forming part of the Smithsonian collection in Wash- 

 ington. It did not exist in the collection of those ores sent to me by 

 Professor Hill. The hexagonal cleavages are perfect, and one small 

 and very perfect crystal was found, which has been measured by Mr. 

 E. S. Dana. Its reactions before the blow-pipe are perfectly in accord- 

 ance with those of the species. It contains no selenium and only a trace 

 of gold. 



Auriferous hessite. — This mineral has been spoken of as petzite ; but 

 it contains much too little gold for this latter species.* Its specific 

 gravity is 8.6 ; luster splendent when freshly broken ; fracture conchoi- 

 dal, brittle, but somewhat malleable j under the pestle laminates into 

 thin scales, and is with difficulty reduced to fine powder, leaving on the 

 agate surfaces metallic streaks of plumbago-like color. Color telluric, 

 tarnishes blackish on exposure, sometimes irridescent. Cleavage none. 



Before the blow-pipe in the closed tube, the pure mineral (with no 

 trace of pyrite) decrepitates, fuses to a globule adhering to the glass, 

 and exhales a white sublimate, fusing into clear, colorless globules. 

 Alone on coal, in both flames, it gives a globule, coats the coal with the 

 characteristic areola of tellurium and tellurous acid ; it does not exhale 

 any odor of selenium, nor show any trace of lead. The globule is non- 

 magnetic if pyrite is absent, and does not vegetate with silver as hes- 

 site does with soda ; it gives a large bead of silver, which dissolves in 

 nitric acid, leaving gold in powder. 



*Mr. A. Eilers, M. E., in a notice of the Red Cloud mine, in the Tranpactious of the 

 American Institute of Mining Engineers, vol. i, p. 315, considers it petzite. 

 44 G s 



