Mineralogy of Sky, 91 



two latter having frequently a greenish hue. Besides the decided 

 nodules of prehnite contained in it, the same mineral is intermixed 

 throughout the rock, forming an integral part of it, and often 

 passing into mesotype, as it appears to do in other more decided- 

 instances. It has been said by Haiiy that prehnite has not been 

 found forming an integrant part of rocks ; but as a compound 

 of a similar nature occurs in the Kilpatrick hills near Glasgow, 

 an exception must be made in favour of these instances. I may 

 here add, that a corresponding rock may be seen on the opposite 

 coast of Raasa. 



It is perhaps superfluous to say that nodules of chalcedony, often 

 hollow and containing crystallized quartz, are occasionally found 

 in the trap rocks of Sky, since they are of such common occur- 

 rence in this substance. The cavities are sometimes, in addition, 

 sprinkled with crystals of stilbite, of analcime, and of chabasite. 



Of those mineral substances which are the least frequent in trap 

 rocks, steatite occurs in considerable quantity ; it is tender, and 

 always of a greenish dirty hue. It is sometimes found in very 

 small nodules ; but in other places, as near Dunvegan and in the 

 parish of Kilmuir, it is so abundant that it has been dug up with 

 the intention of exporting it for economical purposes. 



I have already mentioned that epidote is found both in the clink- 

 stone and in the trap, but in too small quantities to render any 

 further account of it necessary. It is thus far worthy of notice, as 

 it is one of the few minerals which seems to appertain to rocks of 

 very different characters and periods of formation. 



The carbonate of lime to which I alluded when speaking of the 

 chabasite, is found in company with this mineral and with the 

 analcime, occupying along with them cavities in the trap : it pre- 

 sents but one form, that rhomb which is called the inverse, and 



M 2 



