56 
CONTRIBUTIONS TO MINERALOGY. 
[bull. 26 
content differentiates it sharply from that mineral, durdenite yielding 
over 10 per cent. 
After deducting '22. 14 per cent of gangue containing over 90 per 
cent of silica, three portions of from 0.15 to 0.20 gram net weight 
each gave the following results: 
l. 
2. 
3. 
Mean. 
Ratios. 
Te0 2 
Fe 9 0, 
70. 83 
22. 67 
71.80 
22.81 
4.82 
.34 
.58 
70.20 
22.79 
70. 71 
22. 76 
.21 
4. 54 
.34 
.56 
.88 
3. 16 
1.00 
H 2 at 100° 
| 4. 68 
H 2 above 100° 
1. 77 
P„(\ ! 
A1,0, 
.54 
Si0 2 , etc." 
100. 00 
a Includes alkalies, traces of magnesia and gold, and a small amount of a metal or metals precii 
table by hydrogen sulphide whose identity could not be established. 
„ 
Allowing the alumina to offset the P 2 5 , though it may belong t 
a soluble silicate or to the tellurite, and a small portion of iron he 
demanded for the P 2 5 , the ratios given in the final column result. 
Thej r are as unsatisfactory as those afforded by the original emmons4 
ite, which were for Fe 2 3 to Te0 2 , 1:3.65 in the original description 
and 1:3.75:1.82 for Fe 2 3 :Te0 2 :H 2 if the supplementary determi- 
nations in Am. Jour. Sci., vol. 10, p. 81, 1899, are accepted. The pres- 
ence of tellurite in association with the green mineral suggests a possible 
explanation of the failure to obtain a simple ratio, though such con- 
tamination was not noted in the material analyzed nor on the neigh- 
boring gangue. If this explanation is correct, however, the variation 
from the original emmonsite ratio becomes still more marked. Pro-! 
visionally, the mineral may be regarded as emmonsite. 
The above results are given in some detail, notwithstanding theirij 
inconclusiveness, because of the importance of accumulating data 
regarding the as yet small but interesting group of ferric tellurites, 
and inciting collectors and mining men to careful search for and pres- 
ervation of further material for more extended study. 
Thus far emmonsite, durdenite, and an unnamed mineral froir 
Cripple Creek, described by Knight in Proc. Colorado Sci. Soc. 
vol. 5, p. 66, and affording likewise unsatisfactory ratios, comprise 
the list of natural ferric tellurites, the formula of no one of which car 
be regarded as established bey T ond question. 
