COPPER    MINES    OF    THE    UNITED    STATES ALASKA.  97 
Other  types  of  scientific  but  slight  economic  importance  also  occur — as,  for  example,  the 
leposits  in  the  glance-impregnated  quartzites  of  the  Permian  Red  Beds,  the  impregnated 
shales  adjacent  to  trap  sheets  in  New  Jersey,  the  Blue  Ridge  deposits  of  Virginia,  etc. — 
)ut  they  need  not  be  considered  here. 
The  class  first  named,  the  contact-metamorphic  deposits,  yield  about  one-fifth  of  the 
iotal  copper  produced  in  this  country.  The  allied  disseminated  ores  yield  about  50, 000, 000 
>ounds,  excluding  Butte's  production.  The  Michigan  production  of  221,000,000  pounds 
or  1905  is  all  from  one  type  of  deposit,  while  the  lenticular  deposits  (d  and  e)  yield 
16,000,000  pounds.  The  grouping  given  above  is  intended  to  express  broad  features  and 
s  not  given  as  a  satisfactory  classification.  Form  is  an  important  factor  from  the  mining 
itandpoint;  mineral  character  of  ore  and  of  gangue  from  the  smelter's  point  of  view. 
The  first  group,  which  for  convenience  may  be  called  the  Morenci  type,  should  really 
nclude  groups  a  and  b.  At  each  of  the  great  mining  centers — Morenci  and  Bisbee,  Ariz.; 
?ananea,  Mexico;  Bingham,  Utah,  and  Ely,  Nev. — the  distribution  of  the  copper  deposits 
s  coextensive  with  a  great  porphyry  stock  and  its  dike  systems.  Areas  devoid  of  intrusions 
i,re  barren.  The  deposits  are  essentially  copper  deposits,  with  very  minor  amounts  of  gold 
tnd  silver.  The  workable  deposits  of  these  localities  occur  either  in  the  limestones  or  in 
he  porphyry.  In  limestone  they  are  confined  to  areas  showing  marked  contact  metamor- 
)hism,  and  the  sulphides  replace  the  original  rock  material,  are  intergrown  with  the 
ontact  minerals,  and  were  introduced  during  the  metamorphism  of  the  limestone.  The 
irevalent  minerals  arc  cupriferous  pyrite  and  chalcopyrite. 
The  disseminated  ores  and  associated  fissure-vein  deposits  carry  pyrite,  with  or  without 
halcopyrite  and  often  with  zinc  blende  and  molybdenite,  with  but  little  quartz  gangue, 
l  altered  porphyry.  The  ores  are  of  low  grade  and  in  many  cases  workable  only  as  far 
own  as  secondary  reconcentration  (enrichment)  has  occurred.  The  porphyry  is  altered, 
sually  greatly  so,  by  late  hydrothermal  action,  in  the  latter  case  consisting  of  sericite, 
uartz,  and  pyrite.  Where  the  fissures  pass  into  other  rocks  alteration  and  ore  deposition 
lso  occur,  except  in  those  already  altered  by  contact  action. 
RECENT   LITERATURE. 
During  the  last  few  years  several  important  papers  describing  copper  deposits  have  been 
lublished.  Among  the  Survey  publications  the  monographs  on  Globe,  Bingham,  Bisbee, 
Encampment  (Wyoming),  and  Morenci  have  appeared  as  Professional  Papers."  Shortei 
.apers  in  Bulletins  Nos.  213,  225,  and  260,  Contributions  to  Economic  Geology,  1902, 
-903,  and  1904,  have  contained  descriptions  of  Butte,  Mont.,  and  the  deposits  of  Shasta 
founty,  Cal.  The  rocks,  but  not  the  ore  deposits,  of  Lake  Superior  have  been  described 
'|y  Irving  in  Monograph  V.  The  copper  deposits  of  eastern  Oregon  are  described  in  The 
Jold  Belt  of  the  Blue  Mountains  of  Oregon,  by  Lindgren.b  The  copper  deposits  of  the 
oeur  d'Alene  district,  near  Mullan,  are  described  by  Ransome  in  a  preliminary  report  in 
tulletin  No.  260,  and  a  more  detailed  paper  is  soon  to  appear.  The  deposits  of  the  eastern 
United  States  are  described  in  a  forthcoming  bulletin. 
ALASKA. 
|  The  first  commercial  shipments  of  copper  from  Alaska  were  made  in  1903,  forming,  it  is 
loped,  the  beginning  of  a  great  industry.  At  the  present  time  the  known  copper  mines  of 
idaska  do  not  warrant  definite  estimates  of  future  production. 
I  On  Prince  of  Wales  Island  two  properties  have  been  brought  to  a  producing  stage  and 
[ire  now  reducing  their  own  ores.  The  first  is  the  Mamie  mine  at  Hadley,  operated  l>y  tl  e 
few  York  Smelting  and  Refining  Company.  The  ore  is  chalcopyrite,  with  pyrite,  a  \<r\ 
[[nail  amount  of  calcite,  and  much  amphibole.  The  ore  occurs  in  lenticular  masses  sur- 
rounded by  black  slickensided  surfaces.     It  is  understood  that  an  arrangement  has  been 
«  Nos.  12,  38,  21,  25,  and  43,  respectively. 
b  Twenty-second  Ann.  Rept.  U.  S.  Geol.  Survey,  pt.  2,  1901,  pp.  551-  776. 
