lOi MANGANESE DEPOSITS OF INDIA : MINERALOGY. [ pART I : 
MnOs combined with each manganate of the general formula R"2Mn05, 
and divide by ^ of the sum of the quantities combined with the manganates 
of the general formula R'''''4(Mn05)3, nearly all these quantities being ob- 
tained in the course of calculating the original analysis into terms of man- 
ganates. These figures work out as follows for each specimen : — 
Amounts of 
MnOs in 
manganates 
of the tj-pe 
Amounts of 
ilnOs in 
manganates 
of the tvpe 
R"'4(ilnb5)3. 
Figures in 
second 
column 
divided bv 
3 
Molecular 
ratio of the 
group 
R"2Mn05 
to the group 
R"'4(Mn05)3. 
Guguldoho- 1 157 . 
Avagudem-A. 372 
Tekrasai-A. 380 . 
Tekrasai-A. 381 . 
Tekrasai-J. 917 . 
40- 10 
36-75 
41- 84 
36-49 
35-84 
6-31 
10-88 
0-65 
8- 37 
9- 96 
2- 10 
3- 63 
0-22 
2- 79 
3- 32 
19- 1 
10- 1 
144-7 
13-1 
10-8 
Taking the general formula of psUomelane as )nR".2^lnO^-}-7iB.'"^ (Mn05)3 
it is seen that, if n be unity in each case, the value of m in the foregoing 
examples varies from about 10 to 145; but is usually between 10 and 20. 
Rammelsberg, in his Handbuch der Mineralchemie, page 182, (1860), 
regards psUomelane as a combination of potash, baryta, and protoxide of 
manganese, with, peroxide of manganese, corresponding to the formvda 
(Mn,Ba,K2)0.(]\In02)2- In the second edition of his Handbuch der 
Mineralchemie, pages 189-192, (1875), [Penrose], he divides psilomelanes 
into two varieties, namely baryta-psilomelane and potash-psUomelane, 
according to whether the mineral is high in baryta or potash. Dana in 
his System of Mineralogy, 6th edition, page 257, says that psilomelane is 
a ' hydrous manganese manganate in which part of the manganese is 
often replaced by barium or potassitmi, perhaps conforming to H4Mn05', 
giving Laspeyresi as the authority for this formula, and adding that the 
material analysed is generally impure, so that the composition is doubtfiJ. 
The specimens analysed above were apparently pure specimens, so that 
the results of their analysis can be taken as giving the correct composition. 
The above calculations show that this mineral does conform to the formula 
H4Mn05, and that the chief constituents of the basic portion of the 
mineral, in addition to manganese and hydrogen, are either barium or 
potassium, although in one case (A. 372) considerable amounts of iron and 
» Jour. fur. prah. Chtmie, XIII, p. 315, (1876). 
