SKY. MINERALS. 413 



also to add that in one place near Loch Scavig it is 

 BO intermixed with the trap as to form an integrant 

 part of the rock. 



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 presents but one form, that 

 rhomb which is called the inverse, and varies con- 

 siderably in dimensions : it is sometimes white, but 

 most generally of a honey yellow colour, and in either 

 case is of rare occurrence. Irregular modifications of this 

 variety, of a white colour, are also found accompanying 

 the laumonite, and it is remarkable that the very same 

 variety is found intermixed with the laumonite of Brittany. 

 The rarest mineral of those which I discovered in Sky is 

 hypersthene. This occurs at Scavig, in the manner already 

 mentioned, the veins being neither numerous, nor large, 

 nor simple in their composition, since they resemble the 

 containing rocks in the different substances of which they 

 are composed. The most prevailing mixture is however 

 that of hypersthene, with a dark felspar resembling that 

 of Labrador in general aspect, but not possessing its 

 iridescence. This felspar is frequently crystallized, but 

 as the crystals are always completely imbedded, nothing 

 further of their form can be discovered than the outline 

 which is displayed by the fracture : together with the 

 dark felspar, white and glassy felspar also occur in the 

 mixture, and the common opaque white variety is some- 

 times, but more rarely, intermixed with all the other 

 substances. It has been already noticed that these 

 veins are traversed by veins of compact felspar and of 

 basalt, and they are also intersected by veins consisting 

 of common white felspar and quartz, sometimes confusedly 

 intermixed, and at others disposed in the graphic form. 

 This opaque felspar is sometimes distinctly crystallized 

 in cavities. Rarely, mica occurs in the compound, and 

 in one specimen I observed transparent green crystals 



