Chap. IX. ] associated non-manganiferous minerals. 
2l3 
and its presence proved by means of the red lead and nitric acid test. 
No attempt was made to estimate the quantity of manganese present, 
or to find out the form in which it existed. Under the microscope I 
found that the quartz contained a large number of minute liquid inclusions 
similar to those so often found in this mineral. In view of the fact 
that the manganese could be extracted by boiling with, acid and did 
not require a fusion to release it, it seems probable that the manganese is 
present in these cavities as a salt in solution and that it only needs 
sufficiently fine grinding for it to be possible to extract the manganeso 
salts in solution. Probably if water had been used instead of acid the 
result would have been just the same.^ 
The colour of amethyst has also been supposed to be due to manga- 
nese (Dana, page 187), and recently the results of 
Amethyst. ^ . ^ ° , , , o i 
some experiments by M. Berthelot have been 
published showing that this is correct and that the colour can be 
removed by heating the mineral. It is supposed that tne colouring 
matter is present as a manganic compound and that heating 
decomposes this into a manganous compound with the liberation of 
oxygen. It is further stated that the colour can be caused to return by 
submitting the mineral to the influence of radium. No true amethyst 
has been found in association with the manganese-ore deposits of 
India, the nearest approach being the amethystine-rose quartz of 
Sandanandapm'am and the pale amethystine quartz of Guguldoho. 
In the geodes of the Deccan Trap formation, however, amethyst is 
not an uncommon mineral ; but the colouring is often imeven, the 
crystals being patchy or zoned. As a locality may be mentioned 
the railway cuttings on th-? Shikara Ghats in the Seoni district, Central 
Provinces, where I obtained a strongly coloured geode. It does not 
follow, however, that any more are to be readily found at the same 
place ; for the distribution of geodes and the nature of their 
mineral contents seem to be most capricious throughout the Deccan 
Trap formation. 
In the manganese-silicate-rocks of both the kodurite and gondite 
, , series quartz is commonly fomid as an original 
Chalcedony and chert. . / . , , • i , 
mmeral. As the result of the chemical changes 
that have taken place in these rocks, however, there has often 
1 Mr. Blyth has since tried to extract the manganese by using water instead of 
sulphuric acid : but did not succeed in doing so. 
2 C'owp/esiJenrfus.CXLIII, pp. 477-488, (1906); abstract iu Jour. Chem. Soc, XC, 
Part II, p. 803, (1906). 
