GRAMTTE-BI METALLIC    AND    CABLE    MINES,    .MONTANA.  33 
of  the  time.  The  Trout,  Algonkian,  Two  Percent,  and  a  number  of 
smaller  mines,  a  mile  or  two  cast  of  Philipsburg,  were  opened  soon 
after  the  Hope,  and  expensive  reduction  plants  were  built  at  the  set- 
tlements e>f  Hasmark  and  Tower  near  the  mines.  The  annual  pro- 
duction of  the  quadrangle,  however,  was  relatively  small  until  1884, 
when  the  Granite  mine,  controlled  by  C.  D.  McLure  and  associates, 
became  an  important  producer.  A  branch  of  the  Northern  Pacific 
Railway  was  built  from  Drummond  to  Philipsburg  in  1887.  Encour- 
aged by  the  success  of  the  Granite,  a  great  deal  of  prospecting  was 
done  on  various  properties  in  the  district,  but  none  of  these  fulfilled 
the  promise  which  they  seemed  to  show  except  the  Bimetallic,  which 
was  on  the  extension  of  the  Granite  vein. 
The  production  of  the  mines  in  the  Philipsburg  quadrangle  up  to 
the  present  time  is  provisionally  estimated  at  $45,000,000  to  $50,000,- 
000,  more  than  half  of  which  has  come  from  the  Grai  ite  mine. 
GENERAL  GEOLOGY. 
The  greater  portion  of  the  Philipsburg  quadrangle  is  composed  of 
sedimentary  rocks  which  range  in  age  from  Algonkian  to  Cretaceous. 
According  to  the  estimate  of  F.  C.  Calkins  the  thickness  of  the  pre- 
Cambrian  portion  of  the  section  is  from  6,000  to  11,000  feet,  and  that 
of  the  later  formations  from  the  Cambrian  to  the  Cretaceous  is  from 
5,000  to  6,000  feet.  The  thickness  of  the  entire  section  varies  from 
11,000  to  17,000  feet.  Except  for  a  probable  angular  unconformity 
between  the  pre-Cambrian  and  Paleozoic  rocks,  the  beds  are  essen- 
tially conformable  in  dip,  though  unconformities  of  erosion  occur  at 
several  horizons.  The  section,  supplied  by  F.  C.  Calkins,  is  given 
below,  the  thicknesses  being  approximate  and  the  correlations  in  some 
degree  tentative: 
Section  of  sedimentary  rocks  in  the  Philipsburg  quadrangle,  Montana. 
Quaternary:  Feet. 
Fluviatile  deposits,  consisting  chiefly  of  rounded  to  subangular  gravel 
and  sand,  spread  on  valley  bottoms  and  forming  terraces  in  the 
vicinity  of  Philipsburg. 
Glacial  deposits:  Moraines  consisting  mainly  of  granite  bowlders. 
Jurat rias  and  Cretaceous: 
Shales,  sandstones,  and  quartzites,  with  some  thin  beds  of  gasteropocl 
limestone 3,  000  + 
Carboniferous: 
Quadrant(?)  formation:  Mainly  quartzite;  generally  some  red  spotted 
shale  at  base;  near  Philipsburg  a  lower  bed  of  pure  quart /ite 
separated  by  a  layer  of  calcareous  shale,  impure  limestone,  etc., 
from  an  upper  bed  of  less  pure  quartzite  and  sandstone;  fossils, 
locally  in  red  shale  and  limestone 200-500 
Bull.  315—07 3 
