ccvipared w'tlh thofe of Ghiane, ^j^g 



is fo'-ind Incmftcd in a granitic mafs : but though the confii- 

 tuent parts of granite arc found tliere from time to time, it is 

 no lefs certain that the real matrix is nothing eUe than fcld- 

 fpar, as is evidentlv icen in the large mine of Ytterley. The 

 mica and quartz found there form diftintt parts, and do not 

 enter into combination with tlie feldfpar* ; but in general it 

 is a rock of feldfpar_. interfedled by large veins of mica, in a di- 

 redlion almoft perpendicular; and it is in the proximity of thcfe 

 veins that the gadolinite as well as the yttrotantalus muft 

 be fought for. The flrft is generally found attached on one 

 fide to a vein of argenteous mica, and the rtft of its volume 

 enveloped by feldfpar. The fecond never adheres immedi- 

 ately to the mica. The clumps (rogno7is) which it forms, 

 become enveloped with a thin cruft of feldfpar, feparate from 

 the grand mafs by thin ftrata of grayifh black mica. The 

 veins charged with thefe rognons are rarely infulated ; feveral 

 of them are found together, feparated only from each other, 

 and from the principal rock, by fimilar fides of mica. It 

 was thus that I for the mofi: 'part found thefe fubftances 

 placed by nature, and it is very rarely that they are found ia 

 grains difleminated throughout the rock of feldfpar. . 



The largefi; rognons which I found of the ore of the yttro- 

 tantalus had not attained to the fize of a walnut. The 

 fradure of them was granulated, of an iron black colour, with 

 a metallic fplendour. 



Its hardnefs is not confiderable ; it can be fcraped by means 

 of a knife, but with difficulty. 



When powdered it is of a grayifli colour. 



It exercifes no a6lion on the magnet. 



I found its fpecific gravity to be 5"J30; but as it was not 

 poflTible for me to find a piece entirely free from feldfpar, I 

 fufpe^led that its real gravity muft he' a little more conlidor- 

 abfe. 



We {hall terminate this extract bv a (liort view of that 

 part of M. Ekeberg's memoir, which relates to the analyfis 

 of the gadolinite, and the compnrifon of the yttria with 

 ghicine, which in feveral works has been confidcrtd as being 

 of the fame nature. 



Gadolinite, when pure, is fuffiricntly compact to ftrikc 

 fire with flcel. 



It is found cryftallized in an imperfedt manner, like fomt 

 kinds of garnets. 



It contains glucinc. 



• I fpcalc htte only of t\\e mnffcs of the pnncipal reck, without deny- 

 ing tl.t poir.billiy oliim'itig tliere fome fr..^ii cr.u .it «.liich ilie tlirtt fub- 

 Aaocit *tc iiitermixrd. 



BcHdc^ 



