178  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  2(j(). 
The  mines  have  been  worked  spasmodically  since  Roman  times. 
The  output  for  the  year  1901  was  34  tons,  and  for  1902  26  tons,  of 
tin  ore. 
Germany. — The  larger  part  of  the  tin  mined  in  Germany  comes 
from  Saxe-Altenberg,  near  the  Bohemian  border  of  Saxony.  The 
tin  occurs  mostly  in  stockworks  in  "  zwitter,"  and  where  mined  they 
carry  from  one-third  to  one-half  per  cent  of  tin.  The  zwitter  is  com- 
posed essentially  of  quartz  with  chlorite  or  lithia  mica,  and  is  an 
altered  granite  in  which  the  feldspars  have  been  replaced  by  silica. 
With  the  cassiterite  there  occur  nuorite,  wolframite,  molybdenite, 
chalcopyrite,  iron  pyrites,  arsenopyrite,  bismuthinite,  and  bismuth. 
Tungsten  minerals  and  arsenic  are  obtained  as  by-products. 
The  production  in  1903  was  121  tons  of  ore,  valued  at  $13,538. 
Austria. — There  is  a  small  output  at  Graupen,  Bohemia,  a  few 
miles  south  of  Alteiiberg,  under  similar  geologic  conditions.  The 
output  is  not  large.  In  1902  it  was  about  52  tons  of  ore,  valued  at 
$2,154. 
Tin  mines  have  been  worked  in  Bohemia  for  hundreds  of  years, 
and  there  were  formerly  a  considerable  number  of  these  mines,  but 
they  have  been  exhausted. 
Russia. — The  only  deposits  of  tin  known  in  European  Russia  are 
in  Finland.  On  the  north  shore  of  Lake  Lodoga  tin  ores  are  worked 
in  connection  with  copper  ores.  The  principal  deposits  are  in  bodies 
of  sahlite  (a  green,  nonaluminous  pyroxene)  in  granite. 
The  production  is  small,  only  about  4-J  tons  of  tin  being  produced 
in  1902. 
Italy. — Although  there  is  at  present  no  output  from  Italy,  it  has 
in  the  past  produced  a  small  amount  of  tin. 
Tin  ore  was  found  at  Campiglia  Marittima,  Tuscany,  in  connec- 
tion with  beds  of  hematite  in  limestone  of  lower  Jurassic  age.  Up 
to  1894  about  77  tons  of  ore  had  been  produced.  No  production  is 
known  since  that  time. 
AFRICA. 
Tin  has  been  reported  from  a  number  of  places  in  Africa,  but  ow- 
ing to  the  difficulty  of  transportation  and  the  unsettled  state  of  a 
large  portion  of  the  continent,  little  is  known  of  most  of  the  occur- 
rences. 
Swaziland. — Tin  was  discovered  in  western  Swaziland  in  1893. 
both  in  alluvial  ground  and  in  veins,  in  a  country  of  quartz,  horn- j 
blende,  and  talc  schists  intruded  by  granites,  all  cut  by  later  acid 
dikes  in  which  cassiterite  occurs,  accompanied  by  tourmaline,  eschy- 
nite,  monazite,  corundum,  garnet,  and  magnetite.  The  placers  are 
shallow  and  easily  worked  and  a  considerable  amount  of  tin  ore  has 
been  extracted  and  shipped  to  England  for  smelting. 
