ROLKS. 2.)3 



beltled crystals. In granitic porphyry that is very poor in 

 quartz, the feldspathic base is almost granular and laminated.* 



3. Greenstones, Diorite, are granular mixtures of white 

 albite and blackish-green hornblende, forming dioritic porphy- 

 ry when the crystals are deposited in a base of denser tissue. 

 The greenstones, either pure, or inclosing laminae of diallaga 

 (as in the Fichtelgebirge), and passing into serpentine, have 

 sometimes penetrated, in the form of strata, into the old strat- 

 ified fissures of green argillaceous slate,, but they more fre- 

 quently traverse the rocks in veins, or appear as globular 

 masses of greenstone, similar to domes of basalt and porphyry.! 



Hypersthene rock is a granular mixture of labradorite and 

 hypersthene. 



Eiiphotide and serpentine, containing sometimes crystals 

 of augite and uralite instead of diallage, are thus neaily allied 

 to another more Irequent, and, I might almost say, more en 

 ergetic eruptive rock — augitic porphyry. J 



ISIelaphyre, augitic, uralitic, and oligoklastic porphyries 

 To the last-named species belongs the genuine verd-antique^ 

 BO celebrated in the arts. 



Basalt, containing olivine and constituents which gelatin- 

 ize in acids ; phonolithe (porphyritic slate), trachyte, and dol- 

 erite ; the first of these rocks is only partially, and the second 

 always, divided into thin lamina?, wdiich give them an ap- 

 pearance of stratification when extended over a large space. 

 Mesotype and nepheline constitute, according to Girard, an 

 important part in the composition and internal texture of ba- 

 salt. The nepheline contained in basalt reminds the geog- 

 nosist both of the miascite of the Ilmen Mountains in the 

 Ural,§ which has been confounded with granite, and some- 

 times contains zirconium, and of the pyroxenic nepheline dis- 

 covered by Gumprecht near Lobau and Chemnitz. 



To the second or sedimentary rocks belong the greater part 

 of the formations which have been comprised under the old 



* Dafrenoy et Elie de Beaumont, Giologie de la France, t. i., p. 130. 



t These intercalated beds of diorite play an important part in the 

 mountain district of Nailau, near Steben, where I was engaged ia 

 mining operations in the last century, and with which the happiest as- 

 sociations of my early life are connected. Compare Hoflfmann, in Pog« 

 gendorf '3 Annalen, bd. xvi., s. 558. 



t In the southern and Bashkirian portion of the Ural. Rose, Rcite, 

 bd. ii., s. 171. 



$ G. Rose, Reiie nack dem Ural, bd. ii.. s. 47-52. Respecting the 

 identity of eleolite and nepheline (the latter containing rather the mora 

 lime), see Scheerer, in Poggend., Annalen, bd. xlix., s. 359-381, 



