I 4 LAKE: GEOLOGY OF SOUTH MALABAR. 



haematite gneiss. The haematite seems to take the place of the horn- 

 blende of an ordinary gneiss. 



About six miles east-south-east of Wandur, south of the old Siss- 

 para Ghat road, there is another mass of somewhat similar gneiss. 

 The rock is here composed of small grains of quartz and garnet, with 

 narrow bands of haematite running through it. The garnets are some- 

 times partly decomposed to ferric oxide and most likely the haematite 

 bands are the final result of this decomposition. 



Five miles south of Wandur on the boundary between Porur and 

 Chembreri amsams (just north of the final m of Yerramungalum of the 

 map) there are two bands of ferruginous gneiss. The western one, 

 the direction of which is well marked, runs 30 E. of N. It has once 

 been worked, tunnels having been driven into the softer parts of the 

 rock. The other band is still worked by means of shafts and galleries. 

 The rock in both cases consists of small grains of quartz, garnet, and 

 magnetite, with a variable amount of yellow ochre. Where the 

 yellow ochre is abundant, the rock is soft and easily worked. 



On the road between Mana'rka'd and Pdlghat, in TachambaVa 

 (Tutchumparae) amsam, about two miles south-east of Yeddacoorchy 

 of the map, there is more haematite gneiss. 



Garnetiferous gneiss. — This is more homogeneous than the 

 quartzose gneiss, but bands of more hornblendic rock occur in it. 

 About four miles north of Ang£dipuram,the hill marked Turitiancoon is 

 composed of magnetite gneiss, similar to that found in Porur amsam. 

 This seems to be in the garnetiferous, and not the quartzose, series. 



Quartzo-felspathic gneiss. — This is best developed in the south of 

 the district. Typically it contains very little hornblende, but horn- 

 blendic and micaceous bands are found in it in many places. Occa- 

 sionally garnets occur in this gneiss. 



Lenticular masses of quartz are sometimes found, e.g. t at Cherpal- 

 cheri, and about two miles from Natgalli 1 on the ManaVkcid road. At 

 Natgalli is another mass of quartz which is highly ferruginous and has 

 at one time been worked for iron. 



1 Natgalli lies about half way between Angadipuram and Manarkad. 

 ( 214 ) 



