



KERRERA. MINERALS. 125 



of these substances, they are actually portions of the 

 neighbouring masses and not independent veins, and 

 that if they could be thoroughly traced, they would be 

 found to terminate in them. But as I shall have occasion 

 shortly to re-examine this subject in the other schistose 

 islands where the same substances occur, I shall here 

 terminate the account of the rocks of Kerrera. 



It only remains to enumerate two minerals that I 

 observed here, both of them being more remarkable for 

 the circumstances under which they occur than for their 

 rarity. 



The first of these is red stilbite, which is found occu- 

 pying the fissures of graywacke schist in the vicinity 

 of a trap vein. The specimens are neither large nor 

 decidedly crystallized, yet they admit of no doubt re- 

 specting the nature of the mineral. 



The next is heliotrope, which is found on the ^'ore 

 in fragments and nodules that appear, from their forms, 

 to have been detached from the conglomerate rock. It 

 is possible that this mineral, being an inmate of trap, 

 may exist here in that rock ; but I did not find it in 

 that situation. It is more probable that it appertained 

 to the original rock, from the ruins of which the con- 

 glomerate was formed ; and if it cannot thus lay claim 

 to Kerrera as its native place, it adds one more to the lo- 

 calities which I have on different occasions recorded, of 

 a substance once esteemed rare. 



