Cross and Hillebrand—Cryolite from Oolorado. 293 
quite pure, being opaque and very slightly colored in part by 
oxide of iron e analysis was made merely to prove its 
identity with the prosopite from vein B. 
i Il Ii. IV Vv 
Al 22°09 21°83 22-03 22°28 22°63 21°79 
Ca 17°67 17°87 16°92 1714 16°80 16°84 
a at 0:20 are 0-15 0°35 
Na bas Slee: 0°48 eee 0°48 0-79 
Ka Sa alee aN se regs 0-11 
MG > oo. as 13°64 (13°37) «4. Ay ee ans 
¥ ae. 33°14 33.22 nue 32°30 
86°31 
Loss as oxygen, 13°69 
100-00 
The mean of all the results under analyses I-IV is as follows: 
Al 22°17 
Ca 17°28 
Mg O1T 
Na 04 
H,.0 13°46 
33°18 
86°74 
Loss as oxygen, 13°26 
100°00 
After subtracting from the fluorine an equivalent for the 
calcium, magnesium and sodium, and combining the remainder 
with aluminium, there remains of the latter 14:44 per cent, re- 
quiring 12°65 per cent oxygen, instead of 13:26 per cent found 
y difference. The atomic values appear as follows, after sub- 
Stituting for magnesium and sodium, an equivalent of calcium : 
Al 22°17 + 274 0°809 
Ca 17-98 + 40:0 449 
33°18 + 19° 1-746 
H,0 13°46 + 18° 0°748 t 1-539 3°285 
0 12°65 + 16° 0-791 
The result is unsatisfactory, the ratio of Ca: Al being as 
1: 1-78 instead of 1:2. In none of the material analyzed was 
the slightest trace of kaolinization to be observed, nor any 
closest scrutiny, it became desirable to ascertain what change 
