NOTES  ON  THE  COPPER  MINES  OF  VERMONT. 
By  Walter  Harvey  Weed. 
Copper  mining  in  Vermont,  though  now  almost  at  a  standstill,  was 
for  a  long  period  one  of  the  chief  industries  of  the  State,  and  its  chief 
mine,  the  Ely,  was,  prior  to  the  opening  of  the  Michigan  deposits,  the 
largest  copper  producer  of  the  country.  The  deposits  belong  to  a 
type  that  is  well  known  in  many  parts  of  the  world  and  includes  some 
of  its  most  famous  producers.  They  hav?  not  as  yet  been  studied  in 
detail,  but  a  brief  reconnaissance  was  made  in  September,  1903,  to 
determine  their  character.  The  salient  features  of  the  deposits  visited 
in  this  preliminary  trip  are  presented  herewith.  f 
The  deposits  contain  vast  amounts  of  low-grade  copper  ore  which 
await  the  development  of  some  cheap  method  of  treatment  to  become 
great  producers.  The  ores  present  considerable  variation  in  their 
amount  of  silica,  but  are  of  fairly  constant  mineralogic  character  and 
very  uniform  in  their  percentage  of  copper.  In  fact,  they  are  practi- 
cally identical  in  mineral  and  chemical  composition  with  the  Duck- 
town,  Tenn.,  ores.  While  it  is  true  that  for  many  years  relatively 
high-grade  ores  were  treated  and  shipped  from  the  mines,  the  average 
content  of  copper  is  only  about  3  per  cent,  and  as  the  metal  occurs  as 
copper  pyrite  intimately  mixed  with  pyrrhotite  (mundic  or  magnetic 
iron  pyrite)  the  ore  is  not  in  demand  as  a  source  of  sulphur.  The 
successful  utilization  of  the  sulphur  content  of  the  Ducktown  ore 
proves,  however,  that  the  sulphur  of  these  ores  can  be  recovered. 
These  deposits  occur  in  the  hilly  region  forming  the  eastern  part 
of  the  Green  Mountains,  the  three  principal  localities  being  in  a 
north-south  line  from  7  to  10  miles  west  of  Connecticut  River.  The 
prevailing  rocks  are  crystalline  schists,  the  "calciferous  schists  '  of 
the  earlier  geologists,  flanked  on  the  east  along  the  Connecticut,  and 
on  the  west  near  Montpelier  by  "Huronian"  slates.  A  few  miles 
due  north  of  the  copper  deposits  lies  the  Barre  granite  quarries,  and 
numerous  smaller  intrusions  of  granite  occur  scattered  over  Orange 
County,  while  dikes  of  granite  and  of  dark  and  heavy  basic  igneous 
rocks  are  known  but  are  not  mapped.  The  most  recent  report a  upon 
the  areal  geology  of  the  district  also  locates  numerous  areas  of  horn- 
°Rept.  State  Geologist  Vermont  for  1900-1901,  p.  46. 
