Chap. IV.] 
HOLLANDITE. 
deposit has shown it to be a manganate, which roust b classed under 
hollandite. This type of ore is very fine-grainad and seeros to be 
crystaUine throughout. It ca i be scratched with moderat3 ease with 
a knife and has a brilliant light-grey metallic appearance, so that in th,^ 
sun it glistens almost like burnished silver, although the colour is some- 
what darker than that of this metal. By comparison it was found 
that the nearest approach to its colour could be obtained by looking 
at a piece of alimiinium in ordinary diffused light. This colour 
corresponds very closely to that of the ore as seen in the sun, although 
as seen in the shade alongside the aluminium the manganese-ora 
appears considerably darker. This ore occurs in very large quantities 
in this deposit, sj that many thousand of tons of it must have been 
exported, hence, even from the commercial point of view, hollandite 
is, in India at least, an important mineral. This massive fine-grained 
variety of crvstalline manganate occurs in beds of considerable thick- 
ness and extent, and one may often see, exposed in the quarry, a 
surface of this ore, many square feet in area, the whole of which 
eNhibit:^ the brilliant appearance noticed above. There is also in 
this deposit a large quantity of the uncrystallized manganate, 
psilomelane ; in fact more of it than of the crystalline manganate. 
The first analysis of hollandite was made by Mr. H. .J. Winch on a 
Chemical composi- Specimen having a specific gravity of 4-95, and is 
tion- shown below : — 
This analysis corresponds to the follov.ing formula : — 
?«lBa,MD)2Mn05 + «(Fe,Al)4(Mr05)3. 
or wi(Ba,]VIu)2Mu05 + H(Fe4(Mii05)3, 
according as the alumina be considered an essential constituent or not.^ 
^Mr. T. R. Blyth, Assistant Curator, Geological Survey of India, has examined this 
mineral more carefully than was possible to Mr. Winch in liis rough jungle laboratory 
and finds that it contains, in addition to the constituents found by Mi. Winch, small 
amounts of lime and magnesia and of one of the rarer elements, which has not been yet 
identified. 
The precipitate obtained in Group II on passing HjS has been examined spectro- 
scopically by Prof. Noel Hartky and found to consist chiefly — in addition to sulphur 
— of barium sulphate and titania. fSubsequently Dr. Jlorris Travers examined some 
of the original mineral and found that the M2S precipitate contains traces of second- 
group elements to the extent of one part in 7,000. A careful analysis of the mixed sul- 
phides showed them to consist principally of antimony with traces of arsenic, bismuth, 
and co2^per, the last two in exceedingly minute quantities. 
Manganese peroxide (MnOj) 
Manganese iirotoxide (MiiO) 
Ferric oxide (Fcj O3) 
Alumu'.E. (AI2O3) . 
Baryta (BaO) 
Silica (SiOa) . 
traces 
65-63 
5-12 
10-56 
0 94 
17-59 
99-84 
