38

OUR  MINERAL  RESERVES.

should  be  adaptable  for  crucible  making.  Although  the  deposit  does
not  compare  in  size  with  the  Ceylon  deposits,  it  might  render  material ­
  aid  in  case  of  a  shortage.
The  graphite  deposits  of  the  United  States  are  fully  described  in
a  report  by  Edson  S.  Bastin  on  the  production  of  graphite  in  1913,
recently  issued  by  this  Survey.

FLINT.
In  1913  nearly  $320,000  worth  of  flint  pebbles  was  imported  into
the  United  States,  mainly  from  Denmark  and  France.  In  these
countries  the  flint  occurs  as  irregular  nodules  in  the  chalk  cliffs  that
border  certain  parts  of  the  coast,  and  under  the  impact  of  the  waves
the  hard  flint  nodules  become  freed  from  their  relatively  soft  chalk
matrix  and  are  gathered  in  great  quantities  from  the  beaches  for
shipment  to  various  parts  of  the  world.  After  reaching  their  destination ­
  the  more  irregular  nodules  are  calcined  and  ground  to  a  fine
powder  for  use  in  pottery  manufacture,  but  those  that  have  been  well
rounded  by  the  waves  are  reserved  for  use  in  tube  mills,  their  hardness ­
  and  chemical  inertness  making  them  a  desirable  grinding  agent.
The  cutting  off  of  the  imports  of  flint  pebbles  should  work  no
material  hardship  to  the  pottery  industry,  as  that  industry  uses  only
subordinate  amounts  of  flint  compared  with  the  crystalline  quartz
obtained  in  Connecticut,  New  York,  and  Maryland,  and  as  the  supply
of  the  quartz  is  far  in  excess  of  the  present  demands.  A  cutting  off
of  the  supply  of  rounded  flint  pebbles  suitable  for  tube-mill  use
would  probably  entail  some  inconvenience,  for  so  far  as  is  known  we
have  no  flint  deposits  that  are  comparable  in  both  quality  and  quantity ­
  of  material  with  the  foreign  supplies  or  that  could  compete
with  them  (except  perhaps  locally)  under  ordinary  conditions  of
uninterrupted  foreign  commerce.
On  account  of  the  high  quality  of  the  foreign  flints  and  the  cheapness ­
  with  which  they  can  be  brought  into  this  country,  little  attempt
has  been  made  either  by  the  Survey  geologists  or  by  dealers  in  flint
to  investigate  the  domestic  sources.  Deposits  of  flint  pebbles  have
been  observed  at  several  localities  in  this  country  in  the  course  of  the
geologic  surveys,  but  they  have  seldom  been  examined  with  especial
view  to  the  possible  utilization  of  the  flints  in  tube  mills.  The
information  available  is  therefore  fragmentary  and  may,  at  the  most,
serve  only  as  a  guide  to  further  prospecting  and  testing.
The  principal  localities  at  which  flint  pebbles  have  been  noted  in
particular  abundance  are  all  in  the  Gulf  States.  The  pebbles  occur
mainly  in  gravel  beds,  and  only  part  of  them  are  well  rounded.  In
some  places  the  gravels  are  stained  and  partly  cemented  by  oxides  of
iron,  but  elsewhere  they  appear  to  be  fairly  free  from  iron.