At the “Golden Rule” Mine, on the mother lode near Poverty Hill, in Tuolumne County, I detected in August last the same tellurium minerals which are found at Carson Hill in the Melones. The veinstone here is an argillite, with thread-like veins of quartz crossing the cleavages of the slate, and in these filons of quartz gold is seen in beautiful specimens. It was in this association that I detected two or three small groups of brilliant crystalline plates, identical in appearance and physical characters with the Melones mineral, which has been called Sylvanite, and affording the same blowpipe reactions.
At the Rawhide Rancho, a mine near Jamestown, on the mother lode, of which I have had occasion to make a careful study, there occurs a deposit or shoot of very rich sulphides containing copper, antimony, iron, arsenic, with gold, silver and tellurium. This ore has in general a bronzy, blackish appearance; shows often free gold in scales of a blackish yellow color, and appears to be a kind of fahlerz, or gray-copper ore, the value of which in silver and gold rises to one thousand dollars per ton, (2,000 lbs.) or even higher. Associated with this ore are brilliant sectile, flexible scales of the same tellurium compound which occurs at Stanislaus and Golden Rule, but in the Rawhide Mine intimately blended with the blackish sulphides before-named—occasionally in nests or small bunches with metallic gold. The blowpipe readily detects in this ore antimony, arsenic, tellurium, copper, iron, manganese, lime, magnesia, chromium, aluminum, gold and silver. It is only in portions containing dolomite and the peculiar greenish mineral, so characteristic of the mother lode, that lime, magnesia, alumina, and chromium are detected. In portions of the fahlerz-like mineral which appear nearly pure, the blowpipe detects only antimony, arsenic, copper, iron, and manganese.
Having transmitted characteristic specimens of these ores, with other interesting California species, to Professors Dana and Brush, at New Haven, these mineralogists inform me, by letter just received, that the tellurids above-named appear to be referable to a new species hitherto undescribed, and Prof. Brush proposes to undertake an analysis of it upon the specimens transmitted by me, which are barely sufficient for the purpose. It is a tellurid of silver and gold, containing more silver than gold. Associated with it is a white cleavable mineral which Prof. Brush thinks may prove to be native tellurium; this is in the Melones and Golden Rule specimens.
Hessite. I obtained from the Reist Mine, on the northeasterly end of Whisky Hill, Tuolumne County, a very small crystal corresponding in its physical characters to the extremely rare telluric silver, known to mineralogists as Hessite. It occurs in the auriferous slates to the east of the main vein; the slates being opened here for a width of seventy-five feet as an open cut. My attention was called to the existence of this species at the Reist Mine by Mr. D. T. Hughes, of Tuolumne County, who informed me that there was an interesting mineral species there containing, as he believed, tellurium, and that masses of it, half an ounce in weight, had been obtained some years since. Unfortunately these specimens fell into ignorant hands, and were destroyed in idle attempts to determine the nature of the substance. On visiting the locality, which is within one mile of the Rawhide Rancho, and on the opposite side of Table Mountain, I found that the proprietor was exploring in a different part of the open cut from that where this species was found, the place being under water. Fortunately in a collection of minerals from Whisky Hill, formed by Mr. Williams, one of the proprietors, and preserved in his house there, I was able to detect one small mass of the Hessite which Mr. Williams divided with me. This Mr. Hughes recognized as identical with the larger masses he had obtained at this mine some years since.
Prof. Bush, in his letter to Prof. Silliman, of October 29th, recognizes this species as Hessite. The specimen was associated with native gold which had been amalgamated and heated, but the constitution of the Hessite did not seem to be affected thereby.
“Tellurid of Silver” is mentioned by Blake, in his list of California species, as found by him near Georgetown, in El Dorado County, in 1854, washed from the gold drift, but the parent vein had never been found.—Ross Browne’s Report, 1867, p. 209.
It appears therefore, from the present state of our knowledge, that a compound of gold and silver tellurium belonging probably to a new species has been detected in three localities upon the mother vein, and associated with it in two of these, probably also native tellurium; and that Hessite (the tellurid of silver) has been found in place in one locality and in the drift in another. I have also detected the foliated tellurium in extremely minute quantity in one of the mines at Angels, and I mentioned in a publication, in 1864, its probable occurrence among the ores of the Josephine and Pine Tree Mines of Mariposa. A careful scrutiny will probably detect those compounds of tellurium at other points when the mother vein is opened, as at Blue Gulch, Quartz Mountain, and Whisky Hill. I have already recognized the blackish antimonial copper sulphides at the App Mine and Silver’s Mine, and in the croppings on the surface of Whisky Hill. Indeed it may not be too much to state that these ores appear to be somewhat characteristic of those portions of the mother vein occurring south of Angels, and especially wherever it is inclosed in magnesian rocks.
Genth has named a species Melonite, from Melones Mine, which he says is a tellurid of nickel. I have not been able to recognize this compound among those ores of the Melones, which I have seen.
(b.) Some Mineralogical Features of the Mother Vein.—From the opportunity I have had of studying the mother vein, I arrive at the general conclusion that its mineralogical characteristics vary greatly with the chemical constitution of the rocks which inclose it. Wherever the serpentine or talcose and calcareous rocks from the inclosing walls, or are near it, the mineral contents of the vein are essentially different from those observed where the inclosing rocks are argillites, or syenites and diorites.
These we find at Mariposa, in the Josephine and Pine Tree Mines, at Peñon Blanco, Maxwell Creek, Blue Gulch, Quartz Mountain, Silver’s, Whisky Hill, Rawhide, Chapavele Hill, Carson Hill, Angels, and Placerville—at all which places I have examined the mother lode with more or less care—a peculiar light apple-green mineral, occurring in scales, associated with iron pyrites in small and brilliant pentagonal dodecahedrons and implanted in a gangue of dolomite mingled with quartz. The dolomite is of the variety known as ankerite, and by its decomposition, which seems hastened by the oxidation of the associated pyrites, gives origin to those highly characteristic masses of brown and reddish-yellow iron gossan which form the characteristic feature of the outcroppings of those portions of the mother vein just enumerated. These gossans always retain the bright green mineral before alluded to unchanged, as also cellular quartz which discloses in its rhombic cavities the form of the decomposed crystals of dolomite or ankerite whose removal has left the vacant spaces. Before decomposition this triple carbonate of lime, magnesia, and iron is brilliantly white, and its real chemical character would never be suspected.