268 Dr A. Boue's Observations on 



These elliptical serpentine masses are separated from the talc 

 slates or mica slates, by layers of a singular talcose or brecciated 

 rock. These brecciated rocks remind us of the breccia of 

 basalt and talc-slate, which border some basaltic bed-like veins 

 of talc-slate, near Recoaro, in the Vicentine ; but these brec- 

 cias are never so distinct as those which separate the eupho- 

 tide and the jaspideous rocks near Borghetto in Liguria, which 

 are described by M. Brongniart. 



The nature of serpentine rocks is not every where the same. 

 There are three sets of these rocks, viz. Serpentine^ with dial- 

 lage and diallage roclc ; Hornhlendic serpentines^ with diallag-e, 

 chromate of iron, and diorite or transitimi greenstone ^ (Py- 

 renees) ; and. Serpentine originating from augite rocks^ through 

 a superabundance of magnesia, as those of Inch Columb, disco- 

 vered by Jameson. Of these sets of rocks, the first mentioned 

 are the most common, the last the least frequent. In the se- 

 cond class may be placed those small nests of serpentine includ- 

 ed in the granular limestones of some mica-slate districts, as 

 that of Glen Tilt. No diallage occurs in them, but the lime- 

 stone contains hornblende and augite, and the imbedded masses 

 of precious serpentine may have been produced by the vicinity 

 of granitose or syenitic rocks, as at Canzacoli in the Tyrol, 

 where a Jurassic dolomite limestone has been in this way changed 

 into a granular limestone with serpentine veins. The diallage 

 serpentines are not every where associated with euphotide or 

 diallage rock: thus it is not met with in the small veins ov small 

 beds of serpentine, and even diallage is rare in those serpentines, 

 as in Moravia, at Portsoy, in Transylvania, &c. In the lep- 

 tinite, or even in the granitic gneiss, the serpentine is without 

 diallage ; but there it frequently contains garnets, as at Zoblitz, 

 Grabenhof, Mezeborz, and Jungeroschiz in Moravia. On the 

 other hand, when serpentine occurs in great hills, it is mixed 

 with euphotide or diallage rock, as in the Hartz, Liguria, Ap- 

 penines, Carpathians, Silesia, and north of Europe. It is fur- 

 ther worthy of remark, that these great masses of serpentine 

 are not every where accompanied with those dark diallage por- 

 phyries, with saussurite and diallage and variolites, which are met 

 with in Piedmont, Brian9on, Western Liguria, the Hartz, South- 

 ern Scotland, and England. These variolites bring to recollect 



