THE DISTRICT 0¥ SCHEMNITZ, HUNGARY. 295 



well-known mining-towns of Schemnitz, Kremnitz, and Konigsberg, 

 with numerous populous villages, and the health-resorts of Eisen- 

 bach and Glashiitte, which enjoy a considerable local celebrity. 

 Traversing this area in a diagonal direction from north-east to south- 

 west is the deep valley of the Gran, one of the most considerable 

 feeders of the Danube. 



The lavas which everywhere compose the outer mountain girdle 

 of the Schemnitz district are all of the type intermediate between 

 the acid quartz-trachytes and the basic basalts. In all of them the 

 predominating felspar is plagioclase ; and they therefore belong to 

 the class of igneous rocks now very generally called " andesites," 

 and not to the true or sanidine-trachytes, in which latter the most 

 abundant felspar is always orthoclase. With regard to the exact 

 species of felspar which constitutes the principal portion of the 

 widely spread Hungarian lavas, the researches made by Karl von 

 Hauer, in the laboratory of the Keichsanstalt of Vienna, and those 

 by Prof. Szabo, of the University of Buda-Pest, lead to closely con- 

 cordant results — the former being made by the ordinary analytical 

 methods, and the latter by the application of Bunsen's-flame reactions, 

 in a manner devised by the Hungarian Professor himself for dis- 

 tinguishing the chemical composition of minute quantities of mine- 

 rals contained in rocks*. From the researches of both these in- 

 vestigators it appears that the principal ingredient of the Schem- 

 nitz lavas is a lime-soda felspar, sometimes approaching to the 

 labradorite and at others to the andesine type. These so-called 

 andesite rocks have been further classed by Tschermak and Doelter, 

 according to the additional constituents which distinguish them, into 

 augite-andesites, hornblende-andesites, and mica-andesites. The 

 resemblance of these modern andesite lavas to the old "porphy- 

 rites " of Devonian and Carboniferous age, in Scotland, is very 

 striking ; in the volcano of Santorin, rocks of precisely similar 

 chemical and mineralogical character are being erupted at the 

 present day. 



The most interesting fact with regard to the constitution of these 

 Hungarian lavas, which in the central parts of their masses are 

 often found to assume a very coarsely crystalline and almost granitic 

 character, while their outer portions present a strikingly scoriaceous 

 or slaggy appearance, remains to be noticed. It is that though the 

 predominant felspar in them is always of the basic type, yet they 

 not unfrequently contain free quartz, sometimes in very large pro- 

 portion. This free quartz is in some cases found to constitute large 

 irregular crystalline grains in the mass, just like those of the ordinary 

 orthoclase quartz -trachytes ; but at other times its presence can only 

 be detected by the microscope in thin sections. These quartziferous 

 andesites were by Stache, who first clearly pointed out their true 

 character, styled u Dacites," from the circumstance of their preva- 

 lence in Transylvania (the ancient " Dacia "). They find their 

 exact analogues, among the more ancient volcanic rocks, in the 



* Ueber cine neue Methocle die Felspathe auch in Gesteinen zu bestimmen, 

 von Di\ Josef Szabo. (Hungarian edition, 1873 ; German edition in 1876.) 



