68 CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167. 
which become 
Al 7407 2 
Ca 3712 1 
F ... 1.3354] ? 87 
Hydroxyl 1.5808/ 
if enough calcium and its equivalent in fluorine are subtracted to make 
the ratio Al : Oa exactly 2 : 1, on the not improbable assumption that 
fluorite is present as an admixture, an assumption that had to be made 
also for the Colorado prosopite in order to bring- it into close agreement 
with BrandPs formula. 
There is now a deficiency in the acidic radicals. The figures for Al, 
Oa, and H 2 are undoubtedly very nearly correct, while the fluorine 
may well be a half per cent low, having been determined by the 
Berzelian method, owing to the difficulty of securing complete decom- 
position of the fine powder by a single treatment with sulphuric acid. 
Let it be permitted to balance the basic and acidic radicals by raising 
the fluorine, and to figure the ideal percentages on this basis. These 
become of interest when compared with the corresponding figures for 
prosopite from Altenberg and Pikes Peak as given below: 
Altenberg. 
Pikes Peak. 
Utah. 
Al 
23.37 
16.19 
35.01 
12.41 
12.58 
22.02 
17.28 
33.18 
13.46 
13.41 
22.74 
16.85 
29.95 
16. 12 
14.34 
Ca 
F 
n 2 o 

100. 00 
If the assumptions made in the foregoing are justified, the Utah 
mineral is prosopite, and further evidence is afforded of the correctness 
of the view established by Penfield that fluorine and hydroxyl can 
mutually replace each other in many mineral species, for their relative 
proportions differ materially in the prosopite from the three known 
localities. The correctness of the formula as applied to the Colorado 
and Utah prosopite is, however, predicated, as said, on the unproven 
assumption that the material analyzed contains some admixed fluorite. 
7. Jeffersonite. 
Two brown substances associated with franklinite and other zinc 
minerals from Franklin Furnace, New Jersey, so alike in appearance 
as to have been taken for the same mineral species, were received from 
Mr. George L. English. One was a little duller than the other and 
proved to be a mixture of several minerals, according to Mr.F. L.Ransome 
of the U. S. Geological Survey, largely pseudomorphie after some mica- 
ceous mineral. From Professor Clarke's calculations, based on the fol- 
