XII. A Chemical Analysis of Sodalite, a new Mineral from 

 Greenland. By Thomas Thomson, M. D. F.R.S. E. 

 Felloiv of the Imperial Chirur go-Medical Academy of Pe- 

 ter sburgh. 



[Read Nov. 5. 1310.] 



THE mineral to which I have given the name of Sodalite f 

 was alfo put into my hands by Mr Allan. In the 

 Greenland collection which he purchafed, there were feveral 

 fpecimens of a rock, obviouily primitive. In the compofition 

 of thefe, the fubftance of which I am about to treat, formed a 

 conflituent, and, at firft appearance, was taken for felfpar, to 

 which it bears a very linking refemblance. 



This rock is compofed of no lefs than five different foflils, 

 namely, garnet, hornblende, augite, and two others, which form 

 the pafte of the mafs. Thefe are evidently different minerals ; 

 but in fome fpecimens, are fo intimately blended, that it requi- 

 red the fkill of Count Bourn on to make the difcrimination, 

 and afcertain their real nature. Even this diftinguifhed mine- 

 ralogift was at firft deceived by the external afpecl, and confi- 

 dered the pafte as common lamellated felfpar, of a greenifh co- 

 lour. But a peculiarity which prefented itfelf to Mr Allan, 

 in one of the minerals, induced him to call the attention of 

 Count Bournon more particularly to its conftruction. 



On a clofer examination of the mineral, M. de Bournon 

 found that fome fmall fragments, which he had detached, pre- 



3 C 2 fented 



/ 



