CRrSTALLISED GJDOLINlTE. 351 



The arrangement of Brongniart appears much more ju- 

 dicious ; he has placed it at the commencement of the Earthy 

 Minerals, and afligns as a reafon, that it is unique in its com- 

 pofition ; and if placed in any other fituation, it would interrupt 

 the feries, either in refpect to its compofition or external cha- 

 racters. 



Of the Cryolite I have very little to obferve, in addition to the 

 defcriptions given in the different mineralogical works. The 

 fpecific gravity I found to be 2.961 ; Hauy ftates it at 2.949. 

 Among the various mafles I examined, there was no trace of 

 cryftallization, farther than the cleavage, which is threefold, 

 and nearly at right angles. The mafles broke in two direc- 

 tions, (which may be fuppofed the fides of the prifm), with 

 great facility, leaving a very fmooth furface ', but the tranfverfe 

 cleavage was more difficult, andby no means fo fmooth. Se- 

 veral of the fpecimens being mixed with galena, pyrites, and 

 cryflals of fparry iron-ore, it would appear that the cryolite is 

 a vein-ftone \ but I was not fo fortunate as to find any of it at- 

 tached to a rock fpecimen, fo as to throw light on its geo- 

 gnofiic relations. 



