368 Geological Survey of the Island of Jersey. 



The stratification, in general, is very perfect, though by no 

 means so much so as that of the argillaceous schist. Fibrous 

 malachite is found in small quantities in the green porphyry ; 

 the constant and plentiful occurrence of the black oxide of 

 manganese, in the same, has been already noticed. There is 

 a vein of clay-iron ore in X bay, and the oxide has been 

 found in small detached pieces in different parts of the island. 

 Sulphuret of iron is extensively disseminated in minute grains 

 through the sienite and porphyries ; hence, though water is 

 abundant even in summer, it is not unfrequently contaminated 

 by this mineral. 



Few rocks surpass those of felspar as building materials, of 

 the utmost durability; they are, however, frequently too hard 

 to repay the expense of being worked as squared stones. At 

 Fort Regent, all the ashler was obtained from near the Icho 

 Rock ; the copings, &c, a, from Mount Madou, whilst the 

 rock on the spot only afforded rough materials for coarse 

 work. St. Brelade's church (built 1111) is in existence to 

 this day. 



Breccia. 



Extending from p in Boulay bay to d (a house half a mile 

 from St. Martins, bearing 7° west of the church), thence to e, 

 on the Rozel road, about a quarter of a mile from the church : 

 /is on the St. Catherine's road, about one- third of a mile from 

 the Martello Tower, and r, the extreme point on this side, is 

 nearly in the middle of the bay. It also appears at d, nearly 

 in the centre of the island, interposed between the felspar and 

 argillaceous rocks. It is a well stratified rock. 



From p to Rozel Harbour the planes dip north, from the 

 last mentioned point to La Coupe and Verclut, south ; so that 

 the turn of the saddle is somewhere in Rozel Harbour. The 

 general height of these hills varies from 300 to 200 feet. 



It is overlaid by the felspar rocks in all directions; and 

 although formed of all the ingredients already mentioned, with- 

 out any apparent order of seniority, they are of course to be 

 referred to an earlier date, 



