The LEI (EXTRACTED FROM THE AMERICAN NATURALIST, JANUARY, 1887.) MINERALOGY AND PETROGRAPHY.' Petrographical News.-Mr. G. A. J. Cole' has recently attempted to explain the occurrence in rocks of "hollow spherulites like the lithophysen of Von Richthofen. The principal theories proposed to account for these bodies are discussed, and that one is accepted which regards them as the result of the alteration of spherulites, in preference to the one in which a vesicular origin is assigned them. The present writer thinks that a study of the phenomena attending the alteration of spherulites will explain satisfactorily the occurrence of the hollow spherulites. In many of these there is often found a little patch of felsitic material with a radial structure, and from this Mr. Cole argues that the whole body was once of the same nature, and that the greater part of the original filling has been removed by decomposing agents, probably through the channels afforded by perlitic cracks. He then examines 3 many of the spherulitic rocks of Great Britain and some from localities in Europe and America, and finds that his views are on the whole confirmed.— Professor Milne, in a recent number of the Transactions of the Seismological Society of Japan, states that the lavas of the Japanese volcanoes (one hundred in all, of which forty-eight are still active) are chiefly andesites, the hornblende varieties of which frequently contain quartz. Those containing olivine approximate to basalts, though true basalt is rare. A critical study of these rocks is now being made by members of the Japanese Survey.-A microscopical examination of the volcanic ash ejected during the recent eruption in New Zealand shows it to contain fragments of limpid plagioclase crystals, dark green pleochroic hornblende, sometimes fibrous, and extinguishing at 15°, biotite and a "golden-colored mica" in well-formed crystals of hexagonal outline, pyrite, magnetite, broken pieces of sulphur, and glass containing crystallites arranged in flow-lines. By treatment of the granite-porphyry from Beucha with hydrofluoric acid, and then the residue thus obtained successively with various other acids, Kroustshoff has succeeded in isolating from it small colorless isotropic crystals with glassy inclusions. These crystals possess a specific gravity greater than 3, a refractive index equal to that of garnet or spinel, and show, before the spectroscope, the lines of iron, calcium, magnesium, and aluminium. The author calls attention to the similarity between these crystals and those which he obtained in a like manner from the phonolite? of Olbrück, and 2 Edited by Dr. W. S. BAYLEY, Madison, Wisconsin. Quart. Jour. Geol. Soc., xli., No. 162, May, 1885, p. 162. 3 Ib., xlii., No. 166, May, 1886, p. 183. 4 Vol. x. part 2, Abst. Nature, Nov. 4, 1886, p. 19. 5 J. Joly, Nature, Oct. 21, 1886, p. 595. "Note sur un nouveau minéral accessoire de la roche de Beucha (près de Leipzig). Bull. de la Soc. Franç. de Minéralogie, ix., No. 4, 1886; also Neues Jahrb. für Min., etc., 1886, ii. p. 180. 7 Ib., ix., No. 3. which he believes are members of the spinel group. A mineral very like those above mentioned also occurs in the tonalite from Adamello. The same author, in another paper, describes a peridotite from Goose Bay, in the Straits of Magellan. It consists essentially of olivine and enstatite, with picotite and apatite as accessory minerals, and serpentine, chrysolite, bastite, and magnetite as secondary constituents. The olivine contains gas, liquid and glass inclusions. The fibres of the bastite seem to have been curved by some mechanical agency (pressure). An analysis of a comparatively fresh specimen yielded,— 43.39 2.26 0.35 0.28 10.47 SiO2 Al2O3 Fe2O3 Cr2O Fe(Mn)O MgO CaO H,O 39.89 2.33 1.54 Basalts, pyroxene-andesites, hornblende-pyroxene-andesites, hornblende-mica-andesites, and dacites, very like similar rocks. occurring in the western portion of our own country, are described by Messrs. Hague and Iddings from the Republic of Salvador, Central America. -Certain Pliocene sandstones" from Montana and Idaho, according to Mr. G. P. Merrill,3 consist of pumiceous dust cemented by calcite or clayey material. An analysis of one of these from Little Sage Creek, Montana, yielded Mr. Whitfield, SiO, Fe,O,+A1,03 65.56 64 CaO MgO Na2O KO H2O loss by ignition 18.24 2.58 0.72 2.08 3.94 1.12 6.50 Mineralogical News.-The lithia micas of Maine and the ironlithia micas of Cape Ann, Mass., have been subjected to a very thorough chemical examination by Prof. F. W. Clarke and the gentlemen associated with him in the chemical department of the U. S. Geological Survey. The various types of these minerals, from different localities in the States named, have been analyzed, and the results of these analyses are given in a paper in the American Journal of Science. By supposing fluorine to replace the hydroxyl (HO) group in ortho-silicic acid, a series. of fluo-silicic acids may be obtained as a nucleus upon which to build the formulæ representing the composition of the various lithia micas. For example, if we represent muscovite by R2 AI, then lepidolite might be represented by SiO, -Messrs. Penfield and Harper' have carefully analyzed pure ralstonite from Greenland, and have found it to contain, Upon calculation it was found that the amount of fluorine obtained in the analysis was not sufficient to unite with all the metals; hence these authors assume that the metals which are in excess of the fluorine combine with hydroxyl. If this be true, the composition of ralstonite as calculated from the analysis is as follows: Mg Na K Ca 4.39 4.27 0.12 0.03 Al F OH OH2 and the mineral may be regarded as an isomorphous mixture of (MgNa,) Al,F-2H2O and (MgNa,)Al, (OH),The mineral which best illustrates the power of fluorine to replace hydroxyl in a chemical compound is herderite, which has recently been shown by these same investigators to consist of an isomorphous mixture of CaBeFPO, and CaBe(OH)PO Lucasite, a new variety of vermiculite, from Corundum Hill, Macon County, N. C., is described by Mr. T. F. Chatard3 as a foliated mineral of a yellow-brown color, with eminent basal cleavage and a submetallic, greasy lustre. It dissolves in hydrochloric acid and exfoliates when heated, swelling at the same time to twice its original volume. It is biaxial and negative, with a small optical angle. The well-known garnet pseudomorphs from the Lake Superior region have been examined by Messrs. Penfield and Sperry. According to these gentlemen the alteration of the garnet consists in a slight oxidation of its iron, a decrease of its silica, an almost total disappearance of its manganese and calcium, and an increase in its magnesium, alkalies, and water. The resulting mineral is a ferrous chlorites with a composition approaching that of prochlorite. An examination of a decomposed garnet from Salida, Colorado, yielded the same result. Some very fine pseudomorphs of limonite after pyrite are figured by T. G. Meem in the October number of the American Journal of Science, in which the striations due to the oscillation of the octahedron and icositetrahedron are well preserved. Meteorites. During the past summer quite a number of short articles descriptive of meteorites have appeared in the American Journal of Science. In the June number Mr. W. E. Hidden describes two masses, neither of which was seen to fall. One is a meteoric iron, found in Independence County, Ark. It weighs ninety-four pounds. A curious feature in connection with it. Amer. Jour. Sci., Nov. 1886, p. 380. 2 Penfield and Harper, Amer. Jour. Sci., xxxii., Aug. 1886, p. 107. 3 Amer. Jour. Sci., xxxii., Nov. 1886, p. 375. 5 Cf. American Naturalist, Feb. 1886, p. 161. 6 Amer. Jour. Sci., xxxii., p. 274. 4 Ib., Oct. 1886, p. 307. 7 lb., xxxi., No. 186, p. 460. = Cr & Mn C Р S Si is the existence through it of a hole measuring five-eighths of an inch in diameter at its narrowest part. Its composition is Fe=91.22; P=0.16; Co and Ni=8.62; thus belonging to the class holosiderite of Brezína. The second mass is from Laurens County, S. C. Its composition, as determined by Mr. J. B. Mackintosh, is as follows: Fe-85.33; Ni=13.34; Co =0.87; P=0.16. The Widmanstättian lines indicate a regular crystallization. The presence of occluded hydrogen and little masses of ferrous chloride (lawrenceite) in its mass render this meteorite exceedingly interesting. In the October number the same author1 describes a meteor found at Fort Duncan, Maverick County, Texas. It weighs ninety-seven and a quarter pounds, and contains 94.90 per cent. Fe; P=0.23; Ni and Co=4.87. Sp. gr. 7.522. Its peculiarity is the development in it of two series of very fine lines crossing each other at an angle of 70°. Since the publication of the article on the three masses of meteoric iron from Glorieta Mountain, New Mexico, four other pieces of the same meteorite have been found. An analysis by Mr. Eakins, of the United States Geological Survey, of what is supposed by Mr. Kunz3 to be the seventh piece of this meteorite, yielded,-Fe Ni Co Cu Zn 88.76 9.86 0.51 0.03 0.03 -The crystalline structure of meteoric irons has been well worked out by O. W. Huntington, who examined the collection of these bodies belonging to Harvard College. By a very careful investigation of the appearance of the Widmanstättian figures on cleavage faces of the different specimens, and by comparison of similar appearances in the case of many minerals, which, during their crystallization, extruded various impurities (as, for instance, many micas containing magnetite), Mr. Huntington is led to conclude that (I.) many meteoric irons show cleavages parallel to the principal planes of symmetry in the isometric system; (II.) that the Widmanstättian figures and Neumann lines are sections of planes of crystalline growth parallel to the three planes mentioned; and (III.) that the features of the Widmanstättian figures are due to the elimination of incompatible material during the process of crystallization. The results of the investigation strengthen the belief that meteoric irons were thrown off from the sun or one of the fixed stars, and that they have cooled very slowly, while revolving in a zone of intense heat.-A meteoric stone found in Utah, between Salt Lake City and Echo, according to Messrs. E. S. Dana and S. L. Penfield,5 appears under the microscope to consist of spherules of olivine, some of which have a distinct coarsely fibrous structure in consequence of the inclu Amer. Jour. Sci., Oct. 1886, p. 304. G. F. Kunz, ib., III. xxx. p. 235; cf. American Naturalist, Dec. 1885, p. 1214. 3 Ib., xxxii., Oct. 1886, p. 311. 4 Ib., III., xxxii., Oct. 1886, p. 284. 5 Amer. Jour. Sci., xxxii., Sept. 1886, p. 226. |