MINERALOGY-OXIDIZED TELLURIUM COMPOUNDS. 
119 
The mineral occurs as irregular small masses of yellowish green color, which 
often assume mammillary forms, the largest observed being about the size of a pea. 
Doctor Hillebrand says: 
In its optical properties, so far as they were determinable, there is no positive disagreement with those 
reported for emmonsite. Mr. W. T. Schaller reports as follows: 
“There are two cleavages, one parallel to b (010) and another parallel to a form in the orthozone. Axial 
plane parallel to b (010). Bx a perpendicular to a cleavage face in the orthozone. The extinction on the clino- 
pinacoid is inclined 25° to 30° to the vertical axis. 2E is approximately 40°. Double refraction medium, 
and the mineral is nonpleochroic.” 
****** * 
Like emmonsite, the mineral melts at a low heat to a red-brown liquid, but, unlike it, gives on stronger 
heating only tellurous oxide, with no trace of selenium or selenious oxide. Analysis confirmed the absence of 
selenium. Its density, too, differs from that of emmonsite, if the determinations in both cases on scanty 
material are to be depended on. After allowance for gangue the original emmonsite was judged to have a 
density of at least 5, while that of the present mineral is but little above 4.53, after allowing for 24.44 per 
cent of gangue, consisting mainly of quartz and to which the specific gravity of quartz was assigned. 
In its appearance the present mineral would seem to resemble durdenite more than emmonsite, but the 
marked difference in water content differentiates it sharply from that mineral, durdenite yielding over 10 per 
cent. 
After deducting 22.44 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: 
Analysis of emmonsite (?) from Cripple Creelc. 
i. 
2. 
3. 
Mean. 
Ratios. 
TeOs . 
70.83 
71.80 
70.20 
70.71 
3.16 
22.67 
22.81 
22.79 
22.76 
1.00 
HjO . 
( -21 
.21 
1 4.68 
4.82 
HjO+ . 
j 
. 
4. 54 
1.77 
Pj0 5 . 
.34 
.34 
AI.Oj . 
.58 
.54 
RiO*. p.t.p. o .... 
.88 
100.00 
a Includes alkalies, traces of MgO and of gold, and a small amount of a metal or metals precipitable by hydrogen sulphide, 
whose identity could not be established. 
Allowing the alumina to offset the P 2 0 5 , though it may belong to a soluble silicate or to the tellurite and 
a small portion of iron be demanded for the P 2 0 5 , the ratios given in the final column result. They are as 
unsatisfactory as those afforded by the original emmonsite, which were for Fe 2 0 3 : Te0 2 , 1 : 3.65 in the original 
description and 1 : 3.75 : 1.82 for Fe 2 0 3 : Te0 2 : H 2 0 if the supplementary determinations in this journal, 
xl, 81,1899 are accepted. The presence of tellurite in association with the green mineral suggests a possible 
explanation of the failure to obtain a simple ratio, though such contamination was not noted in the material 
analyzed nor on the neighboring gangue. If this explanation is correct, however, the variation from the orig¬ 
inal emmonsite ratio becomes still more marked. Provisionally the mineral may be regarded as emmonsite. 
The above results are given in some detail, notwithstanding their inconclusiveness, because of the impor¬ 
tance of accumulating data regarding the as yet small but interesting group of ferric tellurites and of inciting 
collectors and mining men to careful search for and preservation of material for more extended study. 
Thus far emmonsite, durdenite, and an unnamed mineral from Cripple Creek, described by Knight in 
the Proc. Colorado Sci. Soc., v, 66, and affording likewise unsatisfactory ratios, comprise the list of natural 
ferric tellurites, the formula of no one of which can-be regarded as established beyond question. 
