MAGNETITE    IN    BERKS    AND    LEBANON    COUNTIES,  PA.  189 
(4)  Limestones  and  limy  shales  are  far  more  likely  to  be  replaced 
by  ore  than  clay  shales  or  sandstones. 
(5)  Particularly  favorable  locations  for  ore  are  found  in  masses  of 
limestone  that  lie  between  masses  of  diabase  and  beds  of  strata  that 
are  in  a  marked  degree  less  susceptible  to  the  metamorphosing  influ- 
ence of  the  igneous  rocks. 
(6)  The  most  promising  situations  will  be  found  at  places  where 
the  largest  number  of  the  above  favorable  conditions  occur  in  com- 
bination. 
Many  or  all  of  the  more  favorable  conditions  enumerated  existed 
at  places  where  the  larger  ore  deposits  of  the  Cornwall  type  were 
formed,  and  as  several  of  these  conditions  may  be  fairly  inferred  to 
exist  at  a  few  other  localities,  still  other  deposits  of  iron  ore  may  yet 
be  found  in  the  same  general  field.  With  a  view  to  pointing  out 
these  supposedly  favorable  situations  descriptions  of  the  geologic 
conditions  in  several  districts  along  the  borders  of  the  Newark  belt 
have  been  prepared  and  will  be  presented  in  the  forthcoming  report. 
Bull.  315—07 13 
