20'2 MANGANESE DEPOSITS OK INUlA ! MINEKALOUY. [ParT ll 
double refraction characteristic of sphene. The colour of the mineral 
is not, however, that of ordinary sphene, but more intense. Cross sec- 
tions of the mineral showing diamond shapes, of acute angles measuring 
SO"" to 50^, give the following scheme of pleochroism : — 
Axis of greater elasticity= yellow-green to greenish yellow. 
Axis of lesser elasticity = orange- red and brown-red to almost rose. 
If the mineral be sphene then these axes should be the b and the c axes 
respectively. The tints for these two axe; in deep-coloured varieties 
of sphene are : — 
b = yellow, often greenish, 
C = red with a tinge of yellow, 
i.e., practically the same as given above. A test for manganese 
distinctly showed this element to be present, though only in small 
amount. Mr. Blyth, of the Geological Survey, carefully tested the 
mineral and proved the presence of titanium. The mineral is therefore 
a slightly manganesian variety of sphene, i.e., yreenovite, the mangan- 
esian nature of the mineral accounting for its striking pleochroism. 
Tscheffkinite. 
This is a mineral that was first found in India by Leschenault in 
1817 or 1818. It was first analysed by Langier in 1825 and was for 
some time not given a definite name, but was called the ' mineral de 
Coromandel ' by Beudant in his ' Trait e de Mineralogie'. ^ The name 
' tschewkinite ' was first given to the mineral in 1842 by G. Rose 2 when 
the author investigated a specimen from the second locality for this 
mineral, namely the Ilmen Mountains in the Ural. The Indian mineral 
was later more accurately analysed by Damour .3 For a long time the 
locality of this mineral in India was vaguely given as the coast of 
Coromandel. Mr. F. R. Mallet, however, in 1892,4 in a paper entitled 
' Note on the locality of Indian Tscheffkinite ' , showed that the 
exact locality is probably Kanjamalai hill, 5 miles W.-S.-W. of Salem, 
Madras Presidency. 
Tscheffkinite is a mineral of very complex composition, and, owing to 
the fact that the mineral analysed seems to be in all cases an alteration 
product, the true formula of the mineral is not known. It is classed 
1 Vol. II, p. 652, (1832) [DamiJ. 
2 'Reise nach den Ural MI, (1842) [Dana]. 
3 Bidl. Soc. Gcol. de France, 2ud Ser., XIX, j). .')50, (18G2). 
4 Ree. Geol. Surv. Ind., XXV, i)p. 123-127, (1892). 
