PHOSPHORUS  ORE  AT  MOUNT  HOLLY  SPRINGS, 
PA. 
B}    George  W.  Stose. 
INTRODUCTION. 
Phosphorus  was  formerly  made  solely  from  hones  and  organic  sub- 
stances, and  it  was  not  until  the  last  decade,  when  the  electric furnacd 
was  perfected,  thai  natural  phosphates  were  used  to  any  extenl  in  its 
manufacture.  The  extraction  of  phosphorus  from  mineral  deposits 
brings  the  industry  within  the  scope  of  the  Geological  Survey's 
investigations.  The  mineral  from  which  phosphorus  was  first  ob-' 
tained  was  phosphorite,  or  rock  phosphate,  an  impure  fluophosphatd 
of  calcium,  from  which  soluble  phosphate  fertilizer  is  generally  made  J 
Apatite,  a  fiuophosphate  or  chlorophosphate  of  calcium,  has  been  used 
in  Europe  and  Canada  to  a  small  extent,  hut  wavellite,  or  aluminum 
phosphate,  so  far  as  know  n.  has  not  been  heretofore  used  commercially 
in  the  manufacture  of  phosphorus,  as  the  mineral  docs  not  generally 
oeeiii-  in  minable  quanl it y. 
DISCOVERY  AND  DEVELOPMENT. 
At  the  loot  of  the  northern  slope  of  Soul  h  Mountain,  in  the  vicinity  I 
of  Mount    Holly  Springs,   Pa..  20  miles  southwest   of  Harrisburg,  a 
deposit  of  wavellite  occur-  in  white  clay  associated  with  manganese  I 
andiron  ore-.      For  many  years  iron  mining  was  a  prosperous  indus- 
try along  the  foot  of  the  mountain  in  this  region,  but  owing  to  com- I 
petition  from  the  great  deposits  of  the  West  and  South  it  has  ceased  | 
to  be  profitable  and  the  mines  have  long  been  idle.     The  iron  i<  a 
secondary  product,  having  been  leached  from  the  iron-bearing  shales 
and  limestones  and  deposited  in  the  residual  sand,  gravels,  and  clays 
lying  on  the  limestones  in  the  valley.     Associated  with  the  iron,  in 
general  underlying  it  or  on  the  side  toward  the  mountain,  is  a  body  1 
of  clay,  in  places  highly  colored  and  plastic,  elsewhere  pure  white  or 
cream  colored,  siliceous,  and  less  plastic.     The  extensive  use  of  pure 
white  clay  as  a  filler  for  wall  paper  and  for  other  commercial  purposes 
474 
