THE  MINERAL-PAINT   ORES  OF   LEHIGH  GAP, 
PENNSYLVANIA. 
By  Edwin  C.  Eckel 
During  the  summer  of  1906,  while  the  writer  was  in  southeastern 
Pennsylvania  examining  the  brown  iron-ore  deposits  of  that  region, 
advantage  was  taken  of  a  favorable  opportunity  to  examine  the  well- 
known  " paint-ore"  mines  and  works  near  Lehigh  Gap,  in  Carbon 
County,  Pa. 
Geology  of  the  deposits. — A  typical  section  in  this  district  would  be 
about  as  follows,  from  above  downward : 
Section  containing  paint  ore. 
Feet. 
Black  slates  (Marcellus). 
Clayey  limestone  ("Upper  Helderberg") 0-6 
Clay 0-  1 
Paint  ore 0-  6 
Clay 2-20 
Sandstone  (Oriskany). 
The  paint  ore  is  an  impure  iron  carbonate  containing  considerable 
clayey  matter  and  some  lime  carbonate.  Near  the  surface  it  weathers 
into  brown  oxide  of  iron.  The  "bed"  of  paint  ore  is  not  continuous, 
but  thickens  or  thins,  and  in  places  disappears  entirely.  As  to  its 
continuity  in  depth  no  definite  data  are  available,  but  at  several 
mines  the  ore  is  said  to  thin  markedly  in  depth,  while  the  limestone 
bed  thickens.  These  conditions  can  perhaps  be  interpreted  best  by 
assuming  that  the  u paint-ore"  deposit  is  the  result  of  a  replacement 
of  the  "Upper  Helderberg"  limestone. 
Other  occurrences  of  iron  ore  in  the  vicinity  lead  to  the  same  con- 
clusion. About  one-half  mile  west  of  Millport,  for  example,  the 
Oriskany  sandstone  shows  an  interesting  exposure.  Here  a  white 
residual  clay  is  being  worked  in  or  below  the  Oriskany  sandstone, 
which  itself  has  been  extensively  quarried  for  sand.  The  point  of 
interest  is  that  the  upper  beds  of  the  sandstone  show  replacement  by 
brown  ore  along  bedding  and  joint  planes,  while  in  places  the  replace- 
ment has  affected  the  mass  of  the  rock.  Some  specimens  show  a 
mass  of  brown  ore  inclosing  scattered  grains  of  sand.     Evidently  the 
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