HESS    AND 
<i  RATON. 
OCCURRENCE    AND    DISTRIBUTION    OP    TIN.  169 
porphyry,  and  syenite.  On  the  north  and  south  are  Silurian  slates 
and  sandstones,  the  latter  changed  to  quartzite  near  the  granites. 
The  tin  ore  seems  to  occur  in  the  granites,  generally  as  impregna- 
tions, sometimes  as  lodes  or  veins.  Narrow  veins  and  pockets  of  ore 
occur  in  the  overlying  slates  and  sandstones  along  the  cleavage 
planes.  It  is  from  the  deposits  in  the  sedimentary  rocks  that  the 
larger  part  of  the  alluvial  accumulations  are  believed  to  have  come. 
The  alluvial  deposits  have  about  3  feet  of  bearing  gravel,  with  an 
overburden  of  25  to  35  feet  of  barren  ground.  The  percentage  of  tin, 
taking  the  whole  deposit,  seems  to  be  much  under  0.5. 
The  water  supply  allows  washing  about  eight  months  of  the 
year  in  the  lowlands  and  about  five  months  in  the  higher  districts. 
The  production  in  1903  was  1G,878  tons. 
Billiton. — This  is  an  island  Wing  about  50  miles  east  of  Banka,  on 
which  the  conditions  are  said  to  be  very  similar  to  those  at  Banka. 
The  granites  are  thrust  through  quartzite,  hornblende-schists,  clay 
dates,  quartzitic  sandstones,  and  close-grained  black  siliceous  schists 
)f  Silurian  and  Devonian  age. 
The  tin  placers  have  been  very  systematically  worked.  Prospect  - 
ng  is  done  by  boring,  and  the  land  is  leased  to  Chinese  on  a  basis  of 
le  tin  content. 
The  production  of  Billiton  for  1903  was  4,088  tons  of  tin.  The 
roduction  has  been  diminishing  since  1900,  for  which  year  it  was 
227  tons. 
Sumatra  lies  southwest  of  the  Lakawn  Mountain  axis,  and  is  but  a 
nail  producer  of  tin,  although  some  veins  and  placers  have  been 
3und  there. 
Other   localities. — Tin   also   occurs   on    Carimon    Island,   a    small 
land  in  the  Strait  of  Malacca,  between  Singapore  and  Sumatra,  and 
i  Flores  Island,  about  300  miles  east  of  Java. 
AUSTRALIAN    REGION. 
The  Australian  region,  including  Tasmania,  is  structurally  closely 
nnected  with  the  Malayan  region,  the  mountain  systems  of  eastern 
stralia  uniting  with  those  of  the  East  Indies  and  continuing  south- 
rd  into  Tasmania. 
Tin  occurs  in  these  mountains  in  the  colonies  of  Queensland,  New 
uth  Wales,  Victoria,  South  Australia,  West  Australia,  and  Tas- 
nia. 
he  tin  is  usually  associated  with  granites  supposed  to  be  of  Per- 
an  age,  which  cut  Silurian  slates,  schists,  sandstones,  and  con- 
merates.  It  occurs  in  granitic  dikes,  in  veins  and  stockworks  in 
tik  granite,  and  in  veins  in  the  overlying  sedimentary  rocks,  accom- 
panied by  fluorine  and  tungsten  minerals,  with  arsenic,  copper,  and 
