66 CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. Ibull.167. 
Analysis of tysonite. 
Ce 2 3 .... 
La group . 
C0 2 
CaO 
Fe 2 3 
Na 2 (with traces K 2 and Li 2 0) 
Less O for F . 
a 42. 89 
b 39. 31 
c 28. 71 
.53 
.18 
.11 
d.30 
112. 03 
12.08 
99.95 
a 0.13 per cent Th0 2 ? 
b At. w. 139.7; includes 0.21 per cent soluble in K 2 S0 4 . 
c Mean of 28.86 and 28.56. 
d Approximate. 
Analysis of bastnasite. 
Ce 2 3 
La group (slight loss) 
F 
C0 2 . 
Fe 2 3 
Na 2 (with traces K 2 and Li 2 0) 
H 2 
LessO forF. 
a 37. 71 
b 36. 29 
7.83 
c 20. 03 
.22 
.18 
102. 34 
3.30 
99.04 
a Moan of 37.73 and 37.69; includes .10 per cent Th0 2 ? 
b At. w. 141 ; includes .09 per cent soluble in K 2 S0 4 . 
c Mean of 19.94 and 20.11. 
Neglecting the last three constituents in each case, the ratios become 
for 
Bastnasite R : F, C0 3 = 1 : 2. 94 
Tysonite R : F, C0 3 = 1 : 3.05 
which ratio for tysonite is not changed by allowing for admixed bast- 
nasite. 
The above direct fluorine determinations fully establish the hitherto 
assumed formulas W" F 3 ' for tysonite and R /;/ (F'CCV) for bastnasite. 
6. Prosopite. 
Early in 1896 Mr. George F. Kunz sent for examination a beautiful 
pale green mineral from Utah, supposed to be identical with the green 
