ROCKS. 2/53 



embedded crystals. In granitic porphyry that is very poor 

 in quartz, the feldspathic base is almost granular and lami- 

 nated.* 



3. Greenstones, Diorite, are granular mixtures of white 

 albitc and blackish green hornblende, forming di critic porphyry 

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

 The greenstones, either pure, or enclosing laminae of diaUage 

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

 sometimes penetrated in the form of strata, into the old 

 stratified fissures of green argillaceous slate, but they more 

 frequently traverse the rocks in veins, or appear as globu- 

 lar masses of greenstone, similar to domes of basalt and 

 porphyry.f 



Hypersthene rock is a granular mixture of labradorite and 

 hypersthcne. 



* Euphotide and serpentine, containing sometimes crystals of 

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

 to another more frequent, and I might almost say, more 

 energetic eruptive rock augitic porphyry .J 



Mclaphyre, augitic, uralitic, and oligoklastic porphyries. To 

 the last named species belongs the genuine verd-antique, so 

 celebrated in the arts. 



Basalt, containing olivine and constituents which gelatinise 

 in acids ; phonolithe (porphyritic slate), trachyte, anddolerite ; 

 the first of these rocks is only partially, and the second always, 

 divided into thin laminae, which give them an appearance 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 basalt. The 

 nepheline contained in basalt, reminds the geognosist both of 

 the miascite of the Ilmen mountains in the Ural, which has 



* Dufrgnoy et Elie dc Beaumont, Geoloyie de la France, t. i. p. 130. 



t These intercalated beds of diorite play a.n important part in the 

 mountain district of Xailau, near Steben, where I was engaged in 

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

 ciations of my early life are connected. Compare Hoffmann, in Poggen- 

 tlorff'e Annalen, bd. xvi. g. 558. 



In the southern and Bashkirian portion of the Ural. Rose, Pcise, 

 l>d. ii. s. 171. 



. G. Hose, Reise nacli dem Ural, bd. ii. s. 47-52. Respecting the 

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

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



