May 25, 1883.] 



SCIENCE. 



459 



THE SYNTHESIS OF MINERALS AND 

 ROCKS. 



Synthese des mineraux et des roches ; avec une planclie 

 en pholochromie. Par F. Fuuque et A. Michel- 

 Levy. Paris, Masson, 1S82. 423 p. 8°. 

 The great value of synthesis in anj- depart- 

 ment of scientific inquirj- is undoubted ; but 

 tlie difficulties connected with it are in most 

 cases so discouraging, and the results obtained 

 so unsatisfactory, tliat an additional interest 

 attaches to experiments so brilliantl}' success- 

 ful as those recentl}' performed in Paris by 

 Messrs. Fouqu6 and hivy in the artificial re- 

 production of volcanic rocks. It is to the 

 French that we owe almost every thing that has 

 thus far been accomplished in synthetical min- 

 eralogj- ; and we can but hail with delight the 

 achievements of these two gentlemen, who 

 have added new lustre to the French name bj' 

 carrying the synthesis one step farther. They 

 have produced in the laboratory, not onlj^ a 

 large number of the rock-making minerals, but 

 have produced them in their natural associa- 

 tions, as they go to make up integral parts of 

 the earth's surface. 



The book before us is to a great extent a 

 compilation, giving a bibliography, and a short 

 resume of the processes by which mineral 

 species have thus far been artificially obtained. 

 Valuable as this is for reference, it is in the 

 first eight3' pages of the work that its principal 

 interest lies. Here we are presented with a 

 systematic account of the authors' own ex- 

 periments, which it has heretofore been very 

 difficult to obtain from the numerous short 

 articles scattered through various periodicals 

 ■which have appeared during tlie past four years. 

 The first chapter is a general introduction, 

 containing, first, the five conditions which an 

 artificial product must fulfil in order to be a 

 successful sj'nthesis. Then are noted several 

 circumstances, which, during late years, have 

 been especially conducive to synthetical in- 

 vestigations in the department of mineralogj' 

 and geolog}-, and the great benefit which these 

 sciences have derived from such investigations. 

 A classification of the various methods made 

 use of in the artificial reproduction of minerals 

 follows ; and the chapter closes with an ar- 

 rangement of the crystalline constituents of 

 the earth's crust, for purposes in hand, in four 

 categories, as follows : — • 



1°. Volcanic (basic) rocks; i.e., plagioclase 

 rocks, and those free from felspar. 



2°. Acidic rocks; i.e., those containing 

 quartz or orthoclase (granite, rhyolite, etc.). 



3°. The crystalline scJiists (gneiss, mica- 

 schist, etc.). 



4°. Mineral veins. 



The minerals of the first of these catego- 

 ries, and their natural associations, have nearly 

 all been reproduced by simple fusion ; those 

 of the last, by volatilization or solution. 

 Those of the remaining two categories have 

 not yet been artificially reproduced with entire 

 success. 



The second chapter is devoted to the account 

 of the authors' own experiments, and a dis- 

 cussion of their results. This is preceded by 

 a brief liistory of what had been before accom- 

 plished in this line. Attempts to reproduce 

 mineral associations by means of superheated 

 water had yielded nothing satisfactory-, and 

 even the method of pure igneous fusion, so 

 often tried, had only produced I'esults that 

 caused the most eminent geologists, in most 

 recent years, to declare that Nature must em- 

 ploy far different means in the formation of her 

 lavas than stands at the command of the labo- 

 rator}'. 



The apparatus with which the syntheses 

 were performed was verj- simple. The sub- 

 stances to be fused were placed in platinum 

 crucibles, incased in coverings of fireclay'. 

 These were heated b3^ a blast of ordinarj^ 

 illuminating-gas in a Leclerc and Forquignou 

 furnace. Four grades of temperature were 

 made use of, designated bj' their numbers as 

 follows : — 



No. 1. Melting-point of platinum. Suf- 

 ficient to reduce anorthite, leucite, and olivine 

 to a vitreous mass. 



No. 2. Melting-point of steel, also of all 

 the felspars except anorthite, and of the bi- 

 silicates. 



No. 3. Between the melting-points of steel 

 and copper. P3-roxene and nepheline fuse 

 readilj'. 



No. 4. Where copper fuses with difficulty. 



The associations of various rock-making 

 minerals were readilj- obtained by the employ- 

 ment of the principle, alreadj- well known to 

 Hall, that the fasiiig-point of a crystallized sili- 

 cate is in general higher than that of the same 

 chemical compound in an amorphous state. If, 

 therefore, a melted silicate glass be held for a 

 time at a temperature between the fusing-point 

 of some mineral whose constituents it con- 

 tain, and its glass, crystals of this mineral will 

 form in the molten mass ; now, if the temper- 

 ature be lowered sufficiently-, the next less 

 easily- fusible mineral nia3' be obtained ; and so 

 on. It is then the rule that the minerals crys- 

 tallize out of the magma in the inverse order of 

 their fusibility. This rule is abundantly veri- 

 fied for the class of rocks capable of synthesis 



