cbider,]  CEMENT    RESOURCES    OF    NORTHEAST    MISSISSIPPI.  515 
At  the  top  of  the  Selma  chalk  there  is  about  10  feet  of  a  sand 
rock  cemented  with  lime  carbonate  which  contains  numerous  little 
bivalve  shells.  This  is  the  same  kind  of  stone  as  that  found  7  miles 
east  of  Sucarnoochee.  There  is  no  evidence  of  any  Midway  lime- 
stone anywhere  from  Wahalak  to  the  Alabama  line,  and  this  is 
the  only  place  where  the  sandstone  was  seen  in  Mississippi. 
The  Midway  or  Flatwoods  clay  is  well  shown  near  Scooba,  Miss. 
A  sample  collected  there  was  analyzed  by  W.  S.  McNeil  in  the 
laboratory  of  the  United  States  Geological  Survey.  The  result  is  of 
interest  because  clays  of  this  t}Tpe  occur  everywhere  near  the  western 
edge  of  the  Selma  limestone  area,  and  such  cIsljs  will  be  needed  to 
reduce  the  percentage  of  lime  carbonate  found  in  some  of  the  purer 
samples  of  Selma  chalk. 
Analysis  of  Midumy  clay,  Scooba,  Miss. 
Silica    (Si02) 61.92 
Alumina    (A1203) 19.47 
Iron  oxide  (Fe203) 2.81 
Lime    (CaO) _       .00 
Magnesia    (MgO) 1.98 
Soda    (Na20) .50 
Potash    (H,0) .00 
Loss  on  ignition 12.29 
Samples  of  Selma  chalk  were  taken  from  an  old  rock  quarry  on  the 
southwest  side  of  Bogue  Chitto  Creek,  one-half  mile  east  of  Prairie 
Rock.  This  limestone  differs  from  that  along  Oaknoxubee  River,  in 
vicinity  of  Macon,  in  that  it  is  much  harder.  In  the  unweathered 
state  of  the  Macon  rock  it  is  very  soft  and  noncrystalline.  One  can 
easily  stick  a  pick  into  it.  But  this  limestone  at  Prairie  Rock  is  a 
hard  so-called  "  flint  rock,"  crystalline  in  character,  and  is  used  for 
building  purposes.  The  rock  at  Macon  when  exposed  to  the  weather- 
becomes  as  white  as  chalk;  that  at  Prairie  Rock  weathers  to  a  dirty 
gra}^  and  shows  iron  stains  on  the  weathered  surfaces.  This  is  due  to 
the  oxidation  of  the  iron  sulphide  (pyrites)  which  is  found  in  small 
concretions  in  the  fresh  rock. 
An  analysis  of  the  Prairie  Rock  limestone,  made  by  W.  S.  McNeil 
in  the  laboratory  of  the  United  States  Geological  Survey,  follows. 
It  will  be  seen  that  the  stone  is  a  very  pure  limestone  in  spite  of  the 
manner  in  which  it  discolors  on  weathering : 
Analysis  of  Selma  limestone,  Prairie  RocJc,  Miss. 
Silica    (Si02)    1.13 
Alumina    (A1203)    1         fi8 
Iron  oxide   (Fe203) 
Lime  carbonate   (CaC03)—  98.36 
Magnesium  carbonate    (MgC03) Trace. 
Water „„ .40 
