Chap. XVI.] gondite series : petrology. 
341 
thin layers interbanded with equally thin layers of quartzite or quartz, 
as is so often the case with the rocks free from rhodonite. 
Not unfrequently members of the gondite series contain small ros- 
The imphibole- s^tes of a fibrous mineral, which, when fresh, seems 
bearing members of to vary in colour from greenish grey to white, but 
the series. which is more often altered to a brownish colour, 
usually some shade of chocolate. This alteration is seen imder the 
microscope, to be due to the deposition along cleavage cracks of brown 
and black oxides, probably of manganese and iron. The mineral has not 
yet been critically examined, but is in all probability some variety of the 
amphibole group. It is found more often in the rocks containing 
rhodonite, with which it is sometimes seen under the microscope to be in 
parallel growth, than in those free from this mineral. 
At two locaUties, rhodochrosite has been definitely identified in 
Rhodochrosite h\ rocks belonging to this series ; whilst in many other 
the gondite serie';. cases small quantities of rhombohedral carbonates, 
formed in all probabiUty by secondary changes from the manganese 
minerals with which they are associated, have been noticed in thin sec- 
tions. In the two cases of Gaimukh and Devi, however, the rhodo- 
chrosite may be an original mineral formed at the time of metamorphism 
of the original sediments. 
From the hsts of rocks occurring in the gondite series as given on 
Felspar in the pages 329 and 330, it will seem as if these rocks 
goudite series. frequently contain felspar. Such, however, is not 
the case, for each of the felspathic rocks mentioned has been found at onlv 
one, or at the most two, locaUties. In the Central Pro^^nces at least, 
the felspar bearing members of this series are very rarely found. In the 
Central Provinces the felspar may be either orthoclase or microcline, 
whilst in Jhabua both orthoclase and plagioclase have been noticed. At 
Nanikot only plagioclase has been found and this but rarely. It is this 
rarity of felspar in the gondite series that not only distinguishes it from 
the kodurite series, but is also an argument against the gondite series 
being of igneous origin. 
It will be seen from the list given on page 329 that piedmontite has 
Piedmo.itite cnl- "^^^ been found in the gondite series as represented 
9i*^«j^and woUastonite, in the typical area, namely the Central Provinces. 
e e series. rpj^^ j^gpg^^g ^.}^g piedmontite-bearing rocks, being 
associated with crystalUne limestones, are found quite apart from the 
masses of the gondite series as defined on page 307. In Jhabua and 
