TAYLER ON THE CRYOLITE OF GREENLAND. 347 



few feet from the under wall of gneiss, it is quite pure and white. 

 Within 10 feet, however, of this under gneiss, it again contains 

 the same minerals disseminated ; but is here separated from the 

 gneiss by a vein of dark purple fluor-spar. The gneiss on both 

 sides of the cryolite contains much fluor-spar disseminated. 



The upper part of the cryolite at its junction with the gneiss 

 is much decomposed, leaving many cavities, which contain loose 

 crystals of sparry-iron. At a depth of about 10 feet from the 

 surface the cryolite, although free from foreign matter, assumes a 

 darker colour, and at 15 feet it is nearly black, and more trans- 

 lucent and compact ; and, as the deeper we sank we found. ^ the 

 cryolite became darker, there is reason to believe that below this 

 depth the mineral will be found to be wholly black. As the white 

 cryolite is only found at the surface, and bears evidence of partial 

 disintegration by having lost some of its compactness and trans- 

 lucency, it is reasonable to suppose that the cryolite was originally 

 wholly dark-coloured or black. 



When the black croyolite is heated to redness, it loses about 

 1 per cent, moisture and acid, the whole of its colour, and part 

 of its translucency, becoming perfectly white, like the cryolite at 

 the surface ; and from this fact we may conclude that the white 

 colour of the cryolite at the surface has been produced by a similar 

 cause. I consider it probable that the trap now found at each end 

 of the cryolite has formerly overlain it, heating it superficially, 

 and rendering it white. There are at present no remains of over- 

 lying trap between these two veins, but in this country the trap 

 and allied rocks disintegrate most rapidly from the effects of 

 frost. The cryolite itself has considerably decreased, from this 

 and other causes, for I found a piece of it imbedded in the 

 upper gneiss, more than 8 feet above the highest part of the 

 cryolite, proving that it formerly stood at that height. 



In working the lead vein we sank about 30 feet on the dip of 

 the cryolite ; it probably extends to a great depth, and exists in 

 great quantity. 



The fact of its solitary occurrence in this spot induces specula- 

 tion in regard to its origin. The number of minerals, mostly 

 crystallised, which accompany it, indicate some powerful and 

 long-continued agency to have operated in a limited space. The 

 few facts I have stated may suggest some opinions which may 

 elucidate the as yet ill-understood subject of mineral veins. 



The cryolite has been hitherto applied to few purposes. The 

 Greenlanders were the first to turn it to account, which they 

 did in a curious manner, viz., the manufacture of snuff. They 

 grind the tobacco leaf between two pieces of cryolite, and the 

 snuff so prepared contains about half its weight of cryolite powder. 

 This snuff they prefer to any other. In Europe cryolite has been 

 employed to a limited extent, but the recent discovery of the mode 

 of preparing aluminium will probably render it a valuable ore of 

 that metal. 



