] 38 MANGANESE DEPOSITS OF INDIA : MINERALOGY. [ Part I : 
It is uncertain wlxetter these are three distinct varieties of pyroxene 
as detailed above, or only three stages in a series of pyroxenes 
gradating one into the other. When the rock-slices are ground very 
thin, then they all become very pale in colour so as to look colourless 
at first sight. "VMien so thin it is often very difficult, in fact almost 
impossible, to distinguish them from rhodonite; which is also colourless 
in thin sections and often occurs in the same rocks. When the rocks 
are fresh this is a matter of little consequence, because the pink colour of 
the rhodonite in hand- specimens at once distinguishes it from all the 
others. 
Colourless pyrcxenes. 
In some of the rocks of Jothvad in Narukot there are pyroxenes that 
under the microscope are seen to be colourless, but which do not 
indicate in the hand-specimen that they are rhodonite, the pink triclinic 
pyroxene, which is also colourless under the microscope. The rocks 
in which these occur are very fine-grained, one of them being composed 
of quartz, rhodonite (?), spessartite, sphene, and a rhombohedral carbon- 
ate, probably calcite. The pjnroxene is practically colourless, shows 
marked cleavage and extinction angles up to 38^. It may be only 
one variety of the yellow pyroxene of this locaUty. The other rock 
in which such a pyroxene occurs is composed largely of piedmontite, 
with a good quantity of spessartite and apatite. The pjToxene is colour- 
less to pale pinkish and in one case gave an extinction angle of a ^ c = 42°. 
This might be a variety of the blanfordite type of pyroxene, practically 
free from manganese. It is not known if these colourless pyroxenes are 
manganiferous or not. It does not perhaps necessarily follow that, 
because they occur in rocks that are themselves strongly mangani- 
ferous, therefore they contain more than a trace of manganese. 
JefFer?onite. 
This is a manganese-zinc pyroxene found at Franklin Furnace in 
New Jersey, U. S. A. It is practically a zinc variety of schefEerite. The 
only record of this mineral in India is to be regarded as very doubtful, 
especially as there is, as far as is known, no specimen extant of what was 
originally determined as jeffersonite. This record is contained in the 
catalogue of the Reverend Mr. Muzzy' s collection of Madura rocks and 
mineralsi ; the locality is given in J. H. Nelson's ' The Madura Country ' 
1 E. Balfour, Catal. Govt. Ceut. Museum, Madras ; ' Madura, its rocks and Minerals' , 
p. 4,(1855). 
