Bulletin of the United States Geological SurveyThe Survey., 1894 |
Otras ediciones - Ver todas
Términos y frases comunes
Al-SiO albite anal area anal furrow analcite anorthite Anthophyllite apex apical Archimylacris Back azimuth basal branches Butte Cassville chabazite church spire Colo Conn corner sec costal margin County Creek cross and U. S. G. S. cupola deeply forked dist distal East base Etoblattina externomedian vein Final Rept flagstaff formula Geol Gerablattina highest point Hill inner margin internomedian area Island Kans Knob length of tegmina leucite light-house Longitude Mass mediastinal area Meters middle miles east miles north miles south miles southwest miles west mineral Miss Mont Mound Mount Mountain Mylacris nearly straight northeast northwest Paromylacris Peak Permanent mark Permian pyroxenes R. D. Lacoe ridge River road Rock scapular vein Scudd silicates sinuate southeast species specimen spire Stone marked strongly arcuate sugarhouse sugarhouse chimney summit tegmina timber tourmaline triangulation station trisilicate U. S. G. S. Latitude West base wing
Pasajes populares
Página 15 - ... each one capable of undergoing chemical change by which alteration products are formed, so that in time the rock may become transformed into new substances, quite unlike those which originally existed in it. A knowledge of the processes which thus occur, dependent on chemical structure, should be applicable to the study of the rocks and should ultimately render it possible so to investigate a metamorphosed mass as to clearly indicate its origin. BULLETIN 589. The calcite marble and dolomite of...
Página 98 - Upon this point the phenomenon of uralitization has definite bearing. In this process pyroxene is converted into amphibole, with increase of volume and little or no change of composition. In other words, a complex molecule has been dissociated into simpler molecules — a phenomenon the direct opposite of polymerization. In the face of this evidence it is difficult to see how the current views as to the relative molecular magnitudes of pyroxene and amphibole can be maintained. The pyroxenes must...
Página 15 - SIR: I have the honor to transmit herewith for publication as a bulletin of the State Museum...
Página 93 - Shepard's had made the former a columbate of lime. This identity, strenuously resisted by Prof. Shepard, although on grounds which show a very superficial knowledge of the whole subject, has been completely proved by subsequent analyses, particularly by that of AA Hayes, in Silliman's Journal, vol. xxxii. p. 341, and its station as a columbate of lime, according to one of Shepard's analyses, confirmed. Dana's Mineralogy, one of the arrangements of which is crystallographical, although in the last...
Página 17 - Miueralogical literature is full of faulty records regarding alterations, and many diagnoses need to be revised. Pseudomorphs have been named by guesses, based upon their external appearance, and often a compact mica has been called steatite or serpentine. In every case an alteration product should be identified with extreme care, both by chemical and by microscopical methods; for without such precautions there is serious danger of error. In each instance the supposed fact must be scrupulously verified....
Página 28 - I refer to the matter here since it seems to me fairly reasonable to look щюп some forms of Carboniferous cockroaches as probably imitative and thereby protective. The first cockroach wing ever described was first described as a fern leaf, and in all or nearly all the localities where their remains have been found they are associated with fern-leaves in immense abundance. While searching for
Página 54 - Hitchcock as foliated chlorite, Turners Falls, and a paler pulverulent variety, as earthy chlorite, Springfield. That the mineral is chemically identical with that analyzed by Hawes, and named diabantite by him, is extremely probable in view of their identity in all physical and especially optical properties, and of the monotonous similarity of the many diabase dikes of the Connecticut basin, in which both occur. That the mineral is distinct from delessite, as the word is used by Zirkel, Rosenbnsch,...
Página 16 - In fact, we find the same small range of mineral species occurring under the same associations in thousands of widely separated localities, a few typical forms containing a few of the commonest metals being almost universally distributed. The longer the evidence is considered the more overwhelming the argument for simple silicate structures becomes. Suppose now that for any given silicate the empirical composition has been ascertained, how can its chemical structure be determined...
Página 25 - Itg color is gray, sometimes with a faint reddish tinge, unless when acted on by the weather, when its color is yellowish. It is in indistinct prisms with oblique seams like zoisite, and in radiated or fascicled masses, which are composed of slender prisms. Luster somewhat shining or pearly. It is nearly as hard as quartz, and sometimes makes a slight impression upon rock crystal. Before the blowpipe it blackens, and a small portion melts, when the heat is very great, into a black slag, which is...
Página 16 - ... find in every case a simplicity of composition far removed from the complexity which is popularly assumed. Even on theoretical grounds we should expect simplicity of structure. The mineral silicates are, as a rule, exceedingly stable compounds, while complex molecules are relatively unstable. They are formed in nature under conditions of high temperature, or are deposited from solutions in which many reactions are simultaneously possible: circumstances that are strongly adverse to any great complications...