Dr. Kühn’s paper on the crystalline schists treats principally of gneiss, and offers little that is new. It is mostly occupied with additional evidence of structural and chemical changes due to dynamic metamorphism in the sense of Lehmann. The most noteworthy of these are development and microstructure of fibrolite; production of augen-gneiss from porphyritic granite; development of microcline structure in orthoclase by pressure; secondary origin of microcline, microperthite and micropegmatite; alteration of garnet to biotite and hornblende.
Dr. Sabersky’s paper on the coarse-grained granites or pegmatites is entirely mineralogical, and is devoted principally to elucidating the structure of microcline. The author concludes that the well-known gridiron structure is due, not to two twinning laws (the Albite and Pericline), as has been generally supposed, but to the Albite law alone, in accordance with which the individuals form both contact and penetration twins, like the albite crystals from Roc-tourné, described by G. Rose.
Dr. Romberg’s paper on the Argentine granites is much more extensive than the two preceding. It is embellished by seventy-two microphotographs, many of which admirably illustrate the special points described. He comes to several results of great petrographical significance, the most important of which relate to the origin of quartz-feldspar intergrowths in granitic rocks. He clearly shows that beside the original granite quartz there is also much of a secondary nature present. This is not microscopically distinguishable from the original mineral, but its later genesis is demonstrated by many careful observations on its relation to other constituents. The abundant secondary quartz is regarded as the product of weathering—principally of the feldspar, into which it has a peculiar tendency to penetrate. The extreme sensitiveness of quartz to pressure is emphasized (as it has been by Lehmann and the present writer) and illustrated by undulatory extinction, banding, granulation and even plastic bending around other minerals. Dynamic action is regarded as the efficient cause of the secondary impregnation of feldspar by quartz, and a union of this with weathering of the feldspar as the source of the abundant and complex pegmatitic intergrowths of quartz and feldspar.
These results are important, and they will now doubtless come to be generally recognized. It is, however, of interest to observe in this connection that all which is here announced as new in regard to secondary and “corrosion” quartz was described and figured in even greater detail by Prof. R. D. Irving ten years ago. This does not appear to be known to Dr. Romberg, for he does not allude to it, but anyone who will turn to pages 99 to 124 and plates XIII, XIV and XV of the monograph on the Lake Superior Copper Rocks (vol. 5, U. S. Geol. Survey, Washington, 1883) will find his conclusions stated in almost the same language and with a much wider range of fact and illustration. Dynamic action is not here adduced as a cause for the saturation of feldspar by secondary micropegmatitic quartz, since the Lake Superior rocks show no evidence of having been subjected to pressure, but that the quartz itself has been derived from the leaching of the feldspar substance and that the impregnation is mostly confined to the orthoclase is clearly stated.
Dr. Romberg also demonstrates, in a number of cases, the secondary origin of albite, especially as microperthite, and of microcline. He gives details relating to each of the mineral constituents, and then the effects of pressure and of chemical action on the most important of them. Among many interesting observations but a few can be even mentioned here; such, for instance, as the original character of muscovite in many granites; the alteration of garnet into muscovite; the dependence of the well-known pleochroic halos in biotite and cordierite upon the substance of the zircon which they almost invariably surround, and secondary rutile needles which grow out from biotite into both quartz and feldspar. In one rock occurring in a granite a violet, strongly pleochroic mineral was found, which, in neither composition nor physical properties, agreed exactly with any known species. It seems to be intermediate between andalusite and dumortierite, but, as its individuality is not yet perfectly established, no new name is proposed for it.
G. H. Williams.
The Mineral Industry, its Statistics, Technology and Trade, in the United States and Other Countries, from the Earliest Times to the End of 1892. Vol. I. Edited by Richard P. Rothwell, editor of the Engineering and Mining Journal. 629 pp., 8vo.
This volume is a statistical supplement of the Engineering and Mining Journal, and is published by the Scientific Publishing Co., of New York, 1893. It takes the place of the former annual statistical number of the Engineering and Mining Journal, and it is the first volume of a series which is to be issued annually. The object of the present volume is to make known, as soon as possible after the expiration of the year 1892, the statistics and the various conditions of the mining industry in that year and in previous years. The future volumes will, each year, bring these statistics up to date, and thus the full particulars of the mining industry will be known within a few days of the expiration of every year. The volume is a compilation of articles written by different authors, and the names of these writers are guarantee that the different subjects have been treated by authorities in the departments with which they deal. The editor himself, it is but justice to him to state, has written some of the most important parts of the volume, notably the article on the statistics of gold and silver, and his well-known familiarity with the subjects he discusses renders the reader confident of their accuracy.
The present volume is not confined to the bare presentation of figures of production and consumption of various mineral products, but it treats each individual branch of the mining industry in its various departments; and in this way the volume really represents a series of treatises on the various mining products and the methods of treating them. The production of each material is given not only for the United States but also for foreign countries; the conditions of the American and foreign markets during 1892 and previous years are discussed, while the various uses of the different materials, the history of mining in different districts, the means of transportation, the metallurgical methods of treating different ores, the methods of sampling, and the possibilities of competition in various mining industries are also described. In addition to this, tables of assessments levied and dividends paid by various mining companies are given. The volume ends with a concise statement of the statistics and condition, as well as the extent, of the mining industries of foreign countries. Thus there is presented, in a volume of no excessive size, a complete and concise epitome of the mining industries of the world; and this work was completed almost immediately after the time to which it relates.
The various subjects are treated in the following order: A résumé and tables of statistics of the mineral products of the United States; articles on Aluminum, Antimony, Asbestos, Asphaltum, Barytes, Bauxite, Borax, Bromine, Cement, Chemical Industry, Chromium, Coal and Coke, Copper, Corundum and Emery, Cryolite, Feldspar, Fluorspar, Gold and Silver, Iron and Steel, Lead, Manganese, Mica, Nickel and Cobalt, Onyx, Petroleum, Phosphate Rock, Platinum Group of Metals, Plumbago, Precious Stones, Pyrites, Quicksilver, Salt, Soda, Sulphur, Talc, Tin, Whetstones and Novaculite, Zinc; Tables of Assessments Levied by Mining Companies from 1887–1893; Tables of Dividends Paid by American Mining Companies; Baltimore Mining Stock Market, Boston Mining Stock Market, Denver Mining Stock Market, London Mining Stock Market, Lake Superior Mining Stock Market, New York Mining Stock Market, Paris Mining Stock Market, Pittsburg Mining Stock Market, Salt Lake City Mining Stock Market in 1892, San Francisco Mining Stock Market; Foreign Countries—Austria-Hungary, Belgium, Canada, China, France, Germany, Italy, Japan, Russia, South American Countries, Spain and Cuba, Sweden, United Kingdom of Great Britain and Ireland.