CRTSfALLISED GADOLINIfE. 349 



Specific Gravity, 3.4802. The fpecimen weighed 1136.39 

 grains. Its furface is a little decompofed, and it has alfo 

 fome minute particles of telfpar intermixed with it ; both 

 of which would afFecl the refult in fome degree ; but nei- 

 ther were of fuch amount as to do fo in any confiderable 

 degree. 



Hardness: fufficient to refifl fleel, and fcratch glafs, but 

 not quartz. 



Lustre : fhining, approaching to refinous. 



Fracture : uneven, verging to flat conchoidal. 



Colour : pitch black which I confider velvet black with a 

 made of brown ; when pounded, of a greeniih grey co- 

 lour. 



Figuri- : it occurs cryflallifed. The fimpleft figure, and 

 perhaps the primitive form, is a rhomboidal prifm, whofe 

 planes meet under angles of 120 and 6o°. In fome 

 of the fpecimens, the acute angle is replaced by one 

 face, in others by two, thereby forming fix and eight 

 fided prifms. All the fpecimens I poflels are only frag- 

 ments of cryftals, none of which retain any part of a ter- 

 mination. They occur imbedded in felfpar, probably gra- 

 nite. 



Chemical Characters : before the blow-pipe froths up, 

 and melts but only partially, leaving a brown fcoria ; with 

 borax it melts into a black glafs. When pounded, and 

 heated in diluted nitric acid, it tinges the liquid of a ftraw 

 colour ; and, fome time after cooling, gelatinates. 



The principal diftinguilhing character of the gadolinite, is 

 its forming a jelly with acid, a chara&er belonging to few 

 other minerals. The Mezotype Lazulite, Apophilite, ./Edelite, 

 and Oxide of Zinc, lb far as I know, alone polTels the fame qua- 

 lity j aad it cannot eafily be miftaken for any of them. 



X x 2 It 



