﻿ECONOMIC 
  GEOLOGY. 
  

  

  131 
  

  

  The 
  dykes* 
  traversing 
  the 
  granitoid 
  rocks 
  west 
  of 
  the 
  Corteliar 
  and 
  

   Alicoor 
  hills 
  are 
  more 
  frequently 
  of 
  very 
  dark-greenish 
  grey 
  color, 
  almost 
  

   black 
  sometimes, 
  but 
  with 
  the 
  felspathic 
  crystals 
  recognizable 
  from 
  the 
  

   hornblendic 
  matrix. 
  

  

  The 
  series 
  of 
  large 
  dykes 
  south 
  of 
  Naggery 
  and 
  also 
  those 
  lying 
  

   between 
  Nellatoor 
  and 
  the 
  Alicoor 
  hills 
  have 
  a 
  truly 
  porphyritic 
  struc- 
  

   ture. 
  Some 
  of 
  these 
  are 
  of 
  large 
  size 
  and 
  continue 
  westward 
  of 
  the 
  

   Madras 
  area 
  for 
  many 
  miles. 
  

  

  Economic 
  geology. 
  

   The 
  mineral 
  resources 
  of 
  the 
  country 
  under 
  review 
  are 
  not 
  great, 
  

   but 
  neither 
  are 
  they 
  contemptible. 
  The 
  metamorphic 
  rocks 
  offer 
  

   inexhaustible 
  supplies 
  of 
  useful 
  and 
  ornamental 
  building 
  stones 
  of 
  various 
  

   kinds. 
  

  

  The 
  beds 
  of 
  very 
  hornblendic 
  gneiss 
  occurring 
  at 
  Palaveram, 
  Cudda- 
  

   pary 
  Choultry, 
  and 
  Puttandalum 
  (Bootandalum 
  of 
  map) 
  are 
  largely 
  

   quarried 
  for 
  the 
  manufacture 
  of 
  articles 
  of 
  domestic 
  use, 
  as 
  well 
  as 
  for 
  

   building 
  purposes. 
  The 
  articles 
  made 
  consist 
  of 
  curry 
  stones 
  and 
  

   rollers, 
  and 
  mortars 
  for 
  pounding 
  paddy 
  and 
  other 
  grains 
  and 
  chunam. 
  

   Small 
  troughs, 
  doorsteps, 
  and 
  small 
  flagstones 
  for 
  flooring 
  are 
  also 
  pre- 
  

   pared 
  there. 
  

  

  The 
  quarries 
  of 
  Seven 
  Pagodas 
  and 
  of 
  Tirukarikunum 
  have 
  also 
  

   supplied 
  large 
  quantities 
  of 
  fine 
  building 
  stone. 
  

  

  The 
  granitoid 
  quartzo-felspathic 
  rocks 
  occurring 
  a 
  mile 
  south-west 
  of 
  

   Nundiveram 
  Bungalow 
  offer 
  a 
  very 
  handsome 
  and 
  durable 
  pale 
  yellow- 
  

   ish 
  or 
  pinkish 
  white 
  stone 
  which 
  can 
  be 
  well 
  quarried 
  ; 
  both 
  very 
  large 
  

   and 
  medium 
  sized 
  blocks 
  are 
  obtainable, 
  owing 
  to 
  the 
  favorable 
  position 
  

   of 
  the 
  lines 
  of 
  jointing. 
  

  

  * 
  The 
  trap 
  dykes 
  near 
  Poody 
  Eailway 
  Station 
  show 
  the 
  porphyritic 
  character 
  in 
  per- 
  

   fection, 
  though 
  by 
  no 
  means 
  of 
  a 
  very 
  coarse 
  grain. 
  

  

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