1108 
MANGANESE DEPOSITS OF INDIA : DESCRIPTIVE. [ ParT IV 
The quartzites seen on the north wall were in layers 1 to 2 inches thick 
and varied in character from a coarse vitreous 
quartz-rock to a fairly fine-grained quartzite, 
one layer of which contained abundant tiny reddish garnets. The;3 
quartzites, especially the finer-grained varieties, often contain abundant 
scattered kaolinic patches, corresponding probably to original felspar. 
Tnterbedded with the quartzites were layers of psilomelane h to 1 inch 
thick formed obviously by the replacement of the quartzites. The 
5-foot ore-band shown in the above section expands to 8 feet in the 
middle of the pit. Further east in this pit the dip of the quartzites 
becomes definite— namely 50° to S. side of strike (E.10''-25°N.). In 
some of the ore there are patches of brown and black chert. One 
specimen of felspathic rock undergoing replacement to ore is interesting. 
It consists of a m'xtare of soft black manganese 
Psilomelane concretion ^^j^^^ ^^^-^^ ^^^^-^ ^ ^^^^^^j ^^^^ 
m litliomargic rock. 
globule, Ij inches in diameter, composed almost 
entirely of psilomelane and black oxide arranged concentrically. 
On the unopened ground between the Sonpuram ard Mamidipilli 
workings there is an outcrop of a banded rock 
Banded pvroxenic quartz- _ j x • j. -j. -i-V. r ,. 
^' ^ composed of a pyroxenic quartzite with lighter 
quartzose bands. The dip is SO'' to S. 5°E. 
The outcrop closely resembles some of the waved banded spessartite- 
quartz-rock outcrops of the Central Provinces, but the microscope 
shows the above to be the real composition of this rock. 
20b. Mamidipilli (Middle Mound). 
The Mamidipilli (also known as Itlamamidipilli) excavations are of 
,^ J great interest, as they show a large amount 
Kodunte. ^ . ' i i • 
of apatite-spandite orthoclase-rock (kodunte). 
The two main pits showed a band of this rock partly converted to man- 
ganese-ore. In one place the oie-band was 15 feet thick and consisted 
of a fairly compact mass of psilomelane and pyrolusite containing abun- 
dant remains of quartz and felspar. In this ore were some residual 
patches of kodurite in which the felspar was fairly fresh,, forming a 
granular aggregate, the granules averaging to J inch in diameter. On^ 
