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other claims under the name Melones mine, showed plainly a nickel telluride of reddish-white cast, of color like that of bismuth,' thickly scattered in grains, and showing pronounced cleavage and a brilliant luster. A concentrate was prepared by the aid of cadmium-boro-tungstate solution, and this was then laboriously hand picked by the aid of a powerful glass. There was certainly more than one foreign mineral present, but identification was not possible except as to a little gold and petzite. The chief impurity was a silver mineral, presumably hessite. If so, the analyses seem to indicate also native tellurium. A perfectly pure article could not be extracted because of difficulty in sometimes distinguishing the foreign minerals from the one sought, but it was hoped that an analysis of both the selected and rejected portions would permit of calculating the composition of the nickel mineral with considerable certainty on the reasonable assumption that no impurity had been removed in relative excess over the other or others.

The analyses below represent the composition of (a) the rejected, (b) the original, and (c) the selected material. Analysis b is given chiefly because of the cobalt determination, the nickel being probably a little high. Although but 0.22 and 0.13 grams, respectively, were available for the analyses a and c the data are believed to be more trustworthy on the whole than those of b, hence the figures under d have been obtained by calculation based on c and a only, after reducing them to 100. Under e is shown the theoretical composition of NiTey. Small amounts of iron, traces of copper, and perhaps one or two other elements are omitted, besides the three-fourths to 2 per cent of gold and petzite that remained unattacked by cold dilute nitric acid, in which the nickel mineral is readily soluble.

The specific gravity of b at 22.5 was 7.72, which is probably higher than the true density of the pure nickel telluride.

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1 Under a lens, and to the unaided eye in certain lights, the color appears more bronze yellow.

If hessite and native tellurium constitute the foreign admixture the mineralogical composition of a and c is shown to be as follows:

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There is here indicated a considerable selective separation of the foreign minerals, since the relative proportions of tellurium and hessite are very different in the two mixtures, but the amounts operated on were so small that a very slight actual error in a determination might give rise to this change in the relative proportions of impurities with out affecting materially the ratios found for the components of the nickel telluride. The three analyses taken together point unmistakably to NiTe, as the formula for the latter mineral. The question then arises, Is this Genth's melonite, or is it a new mineral Genth found:

To
Ni
Ag.
Pb..

73. 43
20.98
4. 08

• 72

99, 21

from which, after deducting hessite, altaite, and free tellurium, he deduces the formula Ni, Tez, requiring Te 76.49 and Ni 23 51.

The difference between his and my own analyses is too great to admit of bringing them into accordance, yet I am indisposed to believe that two minerals are represented, for both occurrence and appearance are opposed to such a view. The present mineral is from the same source as Genth's. Its physical characteristics, so far as ascertainable, coincide with those of melonite, and it is called melonite by the people at the mine. Melonite was considered by Genth to be hexagonal on the strength of its eminent cleavage and the observation of a single microscopic 6-sided plate. Mineralogically a hexagonal form in the pyrite group, assuming this mineral to belong there, is not to be looked for, but the evidence in favor of hexagonal crystallization is too meager to permit this to be used as an argument one way or another.

COLORADOITE 1.

One small specimen from the Norwegian mine showed in dolomite, petzite, hessite, and a mercury telluride. Superficially the latter was not to be distinguished from the accompanying petzite and hessite, and

was in insufficient amount to admit of analysis for the determination

of its formula. It however gave the tests noted by Genth for the orig. inal coloradoite from Colorado, and in addition the following character. istic may be noted: On heating with strong nitric acid it becomes coated with a white insoluble salt of mercury, which retards further action of the acid.

It is, in all probability, coloradoite, and if so this is its second known locality of occurrence, though I have been informed that a mercury telluride has recently been found in western Australia.

PETZITE.

One specimen of petzite from the Norwegian mine gave such an abundance of pare material that an analysis seemed desirable. The results were as follows:

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Approximate specific gravity at 23° C., 8.925. The molybdenum may exist as sulphide. The ratios lead almost exactly to the formula Au,Te, 3 Ag Te.

3. HESSITE FROM MEXICO,

As an addition to the foregoing work may be given an analysis of hessite from a new locality-San Sebastian, Jalisco, Mexico-the material having been received from Mr. Frederic Chisolm:

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The only important occurrence of covellite in this country is at Butte, Montana, where it occurs in splendid indigo-blue masses. Specimens from the East Greyrock mine, collected by Mr. George W. Tower,

formerly of the United States Geological Survey, gave almost the theoretical composition as shown below. Specific gravity at 26° C., 4.76, uncorrected for impurities.

An analysis of enargite collected by Mr. Tower in the Rarus mine, at Butte, is also given.

Analysis of covellite.

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These minerals formed a single fine specimen half as large as the fist, without crystal faces, from Cheyenne Mountain, near Pikes Peak, Colorado. The bastnäsite covered one side of the tysonite to the depth of an inch. The line of demarcation between the two minerals was sharp, but examination of their sections by Mr. H. W. Turner showed the tysonite to be permeated by stringers of bastnäsite along numerous cracks and that occasional grains of the latter were embedded in the tysonite, which accounts for the CO, shown in the tysonite analysis. Attached to the tysonite at portions of its surface were other white and brownish alteration products derived from it, as shown by qualitative tests. The tysonite was evidently the remnant of a single large crystal, since, according to Mr. Turner, all parts had the same optical orientation. Mr. Turner further found the optical properties of both minerals, so far as determinable, to agree with those given in Dana's Mineralogy, and the index of refraction of the bastnäsite to be greater than that of the tysonite. He likewise noted in both minerals minute colored inclusions, indeterminable and very trifling in amount, and also in the tysonite “numerous minute angular cavities in which there is a liquid,

often with gas bubble. Minute, clear, cuboidal crystals, apparently isometric, were also noted in some of these cavities.”

The composition of the minerals was found to be as given by Allen and Comstock, with the exception that the ratios of cerium oxide to the oxides of the lanthanum group are not quite the same. The formulæ are not thereby affected.

Cerium was separated from the lanthanum group oxides by two precipitations by potassium hydroxide followed by long introduction of chlorine. After recovery of the earths remaining in solution, they were again subjected to this treatment to be certain of having all the cerium. In one case a sinall portion was thus recovered. The ceriun was most carefully examined for thorium and traces of what appeared to be thoria were found. The other earths were wholly precipitable by potassium sulphate with exception of traces of what may be oxides of the yttrium group. Approximate molecular weight determinations of the combined oxides of these two groups were made, and they show an appreciable difference, which may, however, be due to the uncertainty of the method. It may be mentioned that on ignition of the sulphates of these earths they acted like the old didymium in that they lost exactly two-thirds of their SO, on ignition over the full flame of the Bunsen burner, a fact which would seem to exclude the presence of lanthanum. Their solutions were pink and gave pronounced absorption spectra. The ignited oxides freed from cerium were a dull, dirty brown, which became nearly white on blasting and acquired a distinct bluish cast on ignition in hydrogen. No appreciable reduction in weight followed heating in hydrogen. The material saved is at the disposal of anyone desiring to examine these earths spectroscopically.

Owing to the great difficulty in effecting complete decomposition of the minerals by sulphuric acid at a single treatment, the fluorine was obtained in condition for estimation by fusing with potassium carbonate after mixing with silica in the proportion of 0,6 gram mineral to 1 gram silica.

Fragments of tysonite when held in the blast gave a distinct crimson flame showing the lithium red line, but an alkali determination failed to reveal more than a trace of this element.

Of the bastnäsite very little pure material could be separated, and it was therefore impossible to place with certainty all the loss shown by the analysis, but a portion of it is to be charged to the oxides of the lanthanum group because of an accident.

Specific gravity of the bastnäsite 5.12 at 270 C. and of the tysonite 6.10 at 28° C., which becomes 6.14 when corrected for 2.65 per cent of bastpäsite.

Bull. 16745

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