4:84: W. K Hidden and J. B. Mackintosh — Yttria and 



We tested the columbic acid for titanic acid and tin, but 

 although we obtained small quantities of precipitates they 

 proved to be largely if not altogether columbic acid, and we 

 did not detect the presence of any other substance. Tantalic 

 acid was not looked for. 



Fergusonite, tri-hydrated. — Specific gravity = 4-36-4-48 ; 

 hardness about 5. Color deep brown, almost black, thin edges 

 show a yellowish-brown translucence. Form and exterior 

 appearance same as the species previously described. Streak 

 and powder pale greenish-gray. On ignition turns light-brown 

 but does not glow nor decrepitate like fergusonite. Is decom 

 posed by hydrochloric acid with separation of columbic acid. 



Analysis. 



Oxygen ratio. 



Cb 2 5 42-79 79-95 



UO s 312 3-24 



U0 2 393 2-90 ^) 



ThOo 0-83 0-62 



A1 2 3 0-85 2-49 | 



. Fe 2 3 • 3-75 Atomic weight, 7'03 J- 51-08 



Y 2 3 , etc. 31-36 =121-77 3228 



PbO 1-94 0-87 I 



CaO 2-74 4-89 J 



Ignition HoO. 7-57 42-05) 



110° C. H 2 0-62 V44-69' 



F -. 0-502 Atomic ratio, 2-64) 



100-002 

 Less = F 0-206 



99-796 



Combining U0 3 as before with bases to form B 2 3 , UO„ the- 

 oxygen ratio of the remainder will be 



Cb a O b : P s 3 : ( H ^°) = 79-95 : 47-84 : 44-69 or 5 : 2-992 : 2'795 



This gives the formula Cb 2 5 , R 2 3 , 3H 2 0, or counting bases as 

 RO then R 3 Cb 2 6 (OH, F) 6 . On comparing the properties of 

 the two minerals here described with typical fergusonite we 

 notice a gradation from the one extreme to the other. 



Specific G. Hardness. When heated. 

 Fergusonite R 3 Cb 2 O s 5-838 (?) 



Mono-hydro-fergusonite R 3 Cb 2 0,(OH) 2 5-67 65 Pale olive - green,. 



decrepitates. 

 Tri-hydro-fergusonite R 3 Cb 2 5 (OH) 6 4-36-4-48 5- Light-brown does, 



not decrepitate. 



Of other published analyses of fergusonite that of the Ytterby 

 variety, by Nordenskiold (Dana's System Min., p. 523), corre- 

 sponds to the di-hydrated mineral. Since we find fluorine in 

 the specimens we have analyzed from Texas, we are led to con.- 



