BROWN    IRON    ORES    OF    RUSSELL  VILLE    DISTRICT,  ALA.  155 
Occurrence  and  geologic  relations. — The  irregular  masses  of  ore,  as 
well  as  the  loose  deposits,  are  found  in  pockets  of  varying  richness, 
separated  by  more  or  less  barren  material,  either  directly  upon  the 
Bangor  limestone  or  within  the  overlying  Lafayette  formation.  As 
has  been  stated,  the  surface  of  the  Bangor  limestone  is  irregular,  and 
many  of  the  ore  deposits  seem  to  have  been  segregated  at  places 
where  this  surface  is  most  uneven.  Hollows  or  depressions  in  the 
limestone  appear  to  have  been  favorable  places  either  for  the  pre- 
cipitation of  the  ore  or  for  the  collection  of  ore  debris  that  has  been 
transported  to  the  region  by  wave  or  stream  action. 
According  to  position  the  ore  may  be  divided  into  two  types: 
(A)  masses  that  lie  directly  on  the  Bangor  limestone  or  on  the  clay 
residual  from  the  limestone,  and(B)  loose  ore  that  occurs  higher  up, 
mixed  with  the  Lafayette  loam.  The  ore  of  type  A  is  the  more 
limited  in  extent,  but  usually  the*  richer  of  the  two,  as  it  contains 
gravel  only  in  a  few  cavities  or  cracks  within  the  mass.  In  places 
over  this  ore  and  at  the  base  of  the  loose  loam  and  gravel  of  the 
Lafayette  there  is  a  very  hard,  pebbly  conglomerate  with  siliceous 
iron-oxide  cement.  The  ore  is  medium  to  dark  brown  in  color,  and 
may  be  granular  and  easily  broken  or  may  be  hard  and  composed 
of  large  lumps  cemented  or  welded  together.  Masses  of  ore  com- 
monly cover  or  surround  a  " c\slj  horse"  or  " white  horse,"  which  is 
a  thin  reef  or  pinnacle  of  light-colored  residual  clay  that  grades  into 
the  argillaceous  limestone  below.  The  clay  at  a  few  places  contains 
small  amounts  of  fine-grained  ore  that  may  have  been  compressed 
into  it,  but  care  is  taken  not  to  mine  more  of  it  than  is  necessary, 
for  when  wet  the  clay  is  extremely  sticky  and  can  not  easily  be 
separated  from  the  ore  in  the  washer.  At  many  places  in  the  hol- 
lows of  the. limestone  between  the  " white  horses"  the  ore  is  found 
in  solid  masses  locally  10  to  15  feet  thick  and  containing  but  little 
foreign  matter.  Many  bowlders  and  masses  of  the  ore  contain  cavi- 
ties that  are  partly  or  completely  filled  with  a  fine-grained  white  to 
yellow  clay  or  powder,  the  condition  of  this  filling  depending  on  the 
quantity  of  moisture  present. 
Most  of  the  ore  of  type  B  consists  of  pebbles  and  lumps,  but  it 
also  occurs  in  fragments  of  all  sizes,  ranging  from  a  coarse  sand  to 
bowlders  a  foot  thick.  The  Lafayette  loam  in  which  this  ore  occurs 
commonly  contains  pebbles  of  fossiliferous  chert  and  of  pink  quartz, 
and  these  in  places  enter  into  the  recently  cemented  conglomerate 
that  lies  over  the  ore  of  class  A.  In  certain  places  the  pebbles  of 
ore  have  been  sorted  and  concentrated  by  nature  so  as  to  form  huge 
placer  deposits. 
The  relations  of  the  two  types  of  ore  suggest  that  the  ore  A  was 
accumulated  in  pre-Lafayette  time,  and  that  the  ore  B  was  derived 
from  it  mechanically  in  fragmentary  form  and  worked  up  into  the 
basal  conglomerate  and  loose  gravel  of  the  Lafayette  formation. 
