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Show 106 % For comparison the analysis of a chrysolite coming ., nearest to the green garnet in composition, is given jj in No. II. It was selected from a nnmher of analyses made of chrysolite from different localities, and men- § tioned in Dana's Descriptive Mineralogy. This cbrys- • S olite ( No. II) came from Hecla, in Iceland, aud was ^ analyzed by Dr. A. Genth. It is a remarkable fact that g all the chrysolites analyzed since Strohmeyer have been 3 sbou n to contain nickel and, most of them, also a trace A of cobalt. Chrysolite also forms, as is well known, a * constituent of certain meteoric stones and of basalts. J' Genth maintains that chrysolite is the source from « which talc, slate, aud many of the serpentines have >; been formed, and sustains this assertion by substantial 3, arguments. He says: " In the change of chrysolite into • cT talc and serpentine a portion of the magnesia is eliroi- Jf nated,. which separates either as brncite, hydromag- © nesite, magnesite or dolomite, minerals which occur -~ more or less at the principal serpentine localities. 7' J "• » FROM MOUNT TAYLOR TO THK PLACER MOUNTAINS. CM o .8 Mount Taylor, next to Baldy, of the Santa F6 range- 2 the highest peak in New Mexico- represents an isolated & and ancient colossal volcano which towers above large J portions of the country and is visible for great distances. "£ It has given birth to volcanic floods of gigantic dimen- Z sions, flooding the adjacent valleys, displacing rivers S'i from their beds, and filling them with quite an nnusu- 14 ally hot liquid. One stream of liquid basalt followed 83 % the bed of the Rio San Jos6 for some distance but did £ t not fill it, so that the water of this river still runs in | a its original course, having, however, now on one of its J) § sides a basaltic mass instead of a sandstone wall, as jg o* represented in Fig. 3. ~ || While the basalt occupies the lower portions of Mount c © Taylor and is spread along its base, the top of the mount- I © ain shows a different volcanic product, namely, trachyte. .= jj> It has a reddish- violet matrix, and contains large crys- 4$ tals of sanidine. While this rock is here of great nui- 5 g formity, the basalt occurs in a number of varieties, cons'* taining alternately olivine, leucite, and nepheline- ^ rarely zeolite, although this latter variety is not infre- * o quently met with in New Mexico, among other places « at Cuchilla, on the Rio de Chama, and the cafion of the © Santa F< 5 Creek, a mile below Cieneguilla. The classi- J fication used by Dr. E. Boviky for the basalts of Bobe- " g mia may be applied also to thoBe of New Mexico. lie o distinguishes six varieties: ( 1) magma basalt; ( 2) neph- £ eline basalt: ( 3) leucit basalt; ( 4) feldspar basalt: ( 5) f trachy basalt; and ( 6; tacily basalt. ( American Jour- •? nal of Science, 1873.) J It is a noticeable coincidence that in the San Juan * range, Abiquin Mountains, and Mount Taylor the ba- H g salt occupies the bases and lower terraces of the mountains and ranges, while rhyolite and trachyte occupy the higher portions and the tops of the peaks. There can be only one explanation for this regularity, which is, that basalt fuses at a lower temperature, has a less viscous fluidity, and takes longer to solidify, and therefore flows off in sheets, while the trachyte and rhyolite HI I « g solidify quickly whenever they are ejected, and conse- •'•' a quently compose the crest of the mountains. The more • J silica a rock contains the more difficult is i t l o fuse it, 8 a* a rule. But not only does the difference in the rela-f live positiou of these volcanic rocks strike our attends tion, but also their very frequent association and co- oc-i g currence. In New Mexico we find the basal ta and I fc trachytes so intimately connected with each other that tho supposition is suggested that they came up through the same fissures of the earth's crust, and perhaps in some cases were thrown up together. This possibility is easy of com- * |