158 
MANGANESE DEPOSITS OF INDIA : MINERALOGY. [ PaRT I : 
If the analysis of this mineral be compared with those given for 
richterite and its relatives on page 146, and with that of the theoretically 
pure tremolite, which is as follows : — 
Si02 57-7 
MgO 28-9 
(aO .13-4 
1000 
it will be seen that winchite has affinities with both tremolite and 
richterite. Neglecting the state of oxidation of the iron, winchite is to be 
regarded as a tremolite containing, in addition to magnesia and lime, as 
its base constituents, oxide of iron in considerable quantity with a small 
amount of alkalies and manganese oxide. Or it may be regarded as 
a variety of richterite with the manganese to a large extent replaced by 
iron, and with a smaller amount of alkalies than richterite usually 
contains. The latter is the closer relationship and consequently this 
amphibole is to be regarded as a variety of richterite. The variety of 
richterite to which it shows the closest relationship is astochite, the 
similarity of these two minerals as regards their colours being very 
close. The reason for giving the Indian mineral a distinct name is 
found in its interesting optical behaviour, which is no doubt due to its 
somewhat different composition. As both astochite and winchite show 
blue and violet or lavender colours, it is interesting to note that in 
astochite the MnO ranges from 6-49 to 12-71%, and the FeO is only 0-15 
to 0-21^; whilst in winchite the relative abundance of these two consti- 
tuents is just the reverse, the FeO being 7-06 per cent, and the MnO 
only 0-77^. From this it is not evident which element is the cause of the 
colouration of the mineral, if it bo either of them and not the alkalies.' 
As regards the angle mm"', however, winchite is more closely related to 
tremolite than to a tochite (see page 152). Sometimes varieties of 
winchite are found at Kajlidongri that are white in colour and are then 
indistinguishable in appearance from tremolite. 
1 It is interesting to note, however, that an aziire-blue pyrox .^iie from Middle Gila, 
New Moxico, noted by G. P. Merrill and R. L. Packard in the Amrr. Jour. Sci . XLIII, 
pjj. 279, 280, (1S92), was found to be a variety of di pside containing 111 per cent, of 
FeO, and no other constituents except Si02. MgO. and CaO. The authors ascribe the 
colouration of the mineral to this FeO. Under the microscope, how ever, the mineral is 
colourless. 
