104 Minerals fi-om Greenland, [Feb» 



to know what tlie forms are. In colour, these crystals are grey; 

 they are mixed thioughoiit with minute particles, probably 

 decomposed hornblersde. 



Of the laradlar felspar there was a very great abundance, 

 some of it equal in opalescence to the labradore, though not 

 possessed of the same variety of colour. I found some small 

 fragments of green felspar, like the Siberian ; and of the com- 

 pact variety there were two kinds, the translucent and opake. 

 The colour of the first is greenish white, with a waxy, small 

 splintery fracture : it has some resemblance to the Chinese 

 felspar, of which the fine, porcelain is fabricated. The compact 

 variety is of a whitish green colour, slightly translucent on the 

 edges with a small grained splintery fracture. The granular 

 variety is a substance by no means common ; it is of a brilliant 

 white, with a crystalline texture, not unhke saline marble; but 

 is distinguished from it, and from granular quartz, by the 

 lamellated structure of the grains : it contaias imbedded garnet 

 and augite. 



Sodalite, 



This is one of the substances alluded to as having been 

 analyzed by Dr. Thomson. J must not here neglect to acknow- 

 ledge my obligations to Mr. Ekeberg, the distinguished chemist 

 of Cpsala, who also analyzed this mineral, and most obligingly 

 comm inicated the result of his investigation, In a letter dated 

 4th August, 1810; with which the labours of Dr. Thomson 

 afforded a striking coincidence, as the following comparative 

 statement indicates : — 



Ekeberg. Thomson, 



Silex 36 38-52 



Alumine 32 27*48 



Lime 270 



Soda 25 23-50 



Mur. acid 6-75 3 



Iron -15 1 



Water 2*10 



Loss. 1*70 



The very uncommon proportion of soda which this mineral 

 contains suggested the name to Dr. Thomson, by whom it has 

 been so well described that I find nothing remaining to be 

 added. Tlicre is one circumstance, however, which I cannot 

 pass over here, particularly as it was not noticed by the Doctor, 

 relative to a fugitive colouring, which I observed on breaking 

 up the masses. On the fresh fractures I was very much surprised 

 to find a beautiful rose or purplish pink colour, and the more so to 

 observe, after laying some specimens by, that in the course of a 

 few hours this lively tint wholly disappeared. I had occasion to 



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