120 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
The  ore  consists  of  massive  pyrrhotite,  containing  interspersed  particles  and  stringers 
of  chalcopyrite  and  pyrite,  together  with  minute  quantities  of  galena  and  zinc.  Calcite, 
zoisite,  quartz,  and  occasional  bunches  of  garnet  occur,  with  actinolite  in  some  deposits. 
The  copper  content  averages  about  2.12  per  cent. 
The  deposits  consist  of  long  and  exceptionally  thick  masses  of  solid  ore,  rarely  with  few 
included  slivers  or  horses  of  country  rock.  These  deposits  occur  on  three  lines  of  fracturing 
and  probable  faulting  and  rock  crushing.  They  are  classed  as  replacement  veins,  similar 
to  those  at  Ore  Knob,  N.  C,  and  the  gossan  lead  of  southwestern  Virginia,  but  the  ore  bodies 
are  larger.     Diagonal  faulting  of  the  ore  bodies  has  occurred. a 
DEVELOPMENT. 
The  London  and  Burra  Buna  mines  are  on  the  westernmost  vein,  the  Isabella  on  the 
middle,  and  the  Polk  County,  Mary,  and  Calloway  mines  on  the  southeast  vein  of  the  dis- 
trict. The  Tennessee  vein  lies  west  of  the  last  mentioned  and  there  are  two  smaller  inter- 
mediate ore  bodies. 
The  deposits  are  extensively  worked  by  two  companies — the  Ducktown  Sulphur,  Copper 
and  Iron  Company  (commonly  known  as  the  English  company)  and  the  Tennessee  Copper 
Company.  The  Burra  Burra  mine  of  the  latter  company  is  now  560  feet  deep,  the  ore 
body  maintaining  its  nearly  uniform  dip  (of  60°)  and  thickness  to  the  lowest  workings. 
The  Tennessee  Company  is  preparing  to  erect  an  acid  plant  to  make  low-grade  sulphuric 
acid  out  of  the  fumes  from  the  blast  furnaces. 
The  ore  of  the  different  mines  has  the  following  composition:  & 
Composition  of  Ducktown  ores. 
!  «■ 
2. 
3. 
4. 
2.744 
36.  519 
24.848 
18.548 
7.294 
2.672 
2.556 
.911 
.770 
3.135 
2.79 
43.26 
29.18 
10.01 
6.32 
1.39 
2.56 
1.00 
.69 
2.80 
2.2 
37.5 
30.0 
10.3 
6.2 
1.9 
2.0 
3.9 
3.0 
31.0 
21.0 
Silica 
26.3 
Lime 
6.1 
2.5 
Zinc : 
.8 
4.4 
Manganese 
100.000 
100.00 
The  first  two  columns  represent  the  ores  smelted  by  the  Ducktown  Copper,  Sulphur 
and  Iron  Company;  the  third  and  fourth  columns  the  ores  of  the  Burra  Burra  and  London 
mines,  respectively,  both  being  from  the  same  vein.  It  will  be  seen  that  there  is  consid- 
erable difference  in  the  composition  of  the  ores  from  the  different  parts  of  the  same  ore  body. 
The  Ducktown  ores  are  no  longer  roasted,  but  are  smelted  raw,  in  blast  furnaces,  with 
a  concentration  of  about  7.3  into  1,  forming  a  12  to  20  per  cent  matte,  which  is  resmelted 
with  a  small  amount  of  raw  ore,  quartz,  etc.,  and  raised  to  a  50  per  cent  matte,  which  is 
in  turn  bessemerized. 
aHenrich,  Carl,  Trans.  Am.  Inst.  Min.  Eng.,  vol.  25,  1895,  p.  198. 
bChanning,  J.  Parke,  Pyrite  Smelting,  p.  254.    Freeland,  W.  H.,  Raw  sulphide  smelting  at  Duck- 
town: Pyrite  Smelting,  p.  111. 
