CHAPTER II. 
MINERALOGY. 
General. 
Distribution of manganese in minerals and rocks — Colours of manganese 
minerals — Occurrence of manganese minerals — List of known manganese minerals 
— List of Indian manganese minerals — List of associated non-manganiferous 
minerals — New species and varieties. 
The total number of well-defined minerals yet found in the earth's 
crust, both in its rocks and in its mineral deposits. 
Wide distribution of in round nvunbers about one thousand. Of 
manganese in minerals , , , , , _ ^ , . 
and rocks. these more than 100 contam manganese as an 
essential constituent, whilst many more frequently 
contain it in less important quantities. The consequence is that most 
of the rocks of the earth's crust contain this element, though usually 
only in smaU proportion ; and according to F. W. Clark^ 0*10 per cent, 
of the earth's crust consists of manganese protoxide (MnO), manganese 
ranking as the fifteenth most important element in this respect. 
There are many minerals that ordinarily do not contain this elc' 
ment in appreciable amount. Under somewhat 
ne£°minerak rare circumstances, such as when such minerals 
have been formed in the presence of large quantities 
of manganese compounds, as in the metamorphism of manganiferous 
sediments, a small quantity of manganese may enter into the composition 
of the mineral with a most remarkable efiect on the colour, and therefore 
frequently on the pleochroism, of the mineral, without affecting its other 
properties appreciably. As a very good example of this winchite may 
be mentioned ; this is practically a variety of tremolite, a colourleps 
mineral, but contains smaU quantities of manganese, iron, and alka- 
lies, in addition to the usual constituents. The winchite, instead of being 
white or colourless, is blue or lavender in the hand-specimen, and shows 
very beautiful pleochroism, under the microscope, in shades of Ulac and 
blue. In the same way blanfordite is a pyroxene containing a cer- 
tain quantity of manganese and alkalies ; in the hand-specimen it is of 
a deep crimson colour, whilst under the microscope it shows as beautiful 
pleochroism, in shades of blue, carmine, and lilac, as has been noticed 
W. a. Geol. Surv., BvUetin No. 228, p. 19, (1904). 
