234         i  ONTRIBUTIONS    TO    ECONOMIC    GEOLOGY;  11)0(3,  PART    I. 
the  Newcastle  quadrangle  there  are  a  large  number  of  sedimentarl 
formations,  which  range  in  age  from  Mississippian  (Carboniferous)  U 
Recent.  These  formations  (see  fig.  7)  are  distributed  in  hands  whici 
to  the  north  and  east  of  Newcastle  have  a  north-south  trend,  and  in 
the  immediate  vicinity  of  the  town  and  in  an  area  northwest  of  it 
occur  in  layers  that  course  from  northwest  to  southeast.  As  one 
travels  west  and  southwest,  away  from  the  Black  Hills  central  core 
of  older  rocks,  he  passes  successively  over  younger  and  younger  for- 
mations. The  older  ormations  therefore  lie  northeast  and  east  of 
Newcastle. 
RAW    MATERIALS. 
The  raw  materials  used  in  the  manufacture  of  Portland  cement  are 
limestone  (which  typically  contains  bul  little  magnesium  carbonate! 
and  shale  or  clay.  In  the  vicinity  of  Newcastle  the  Minnekahta 
limestone,  the  Morrison  shale,  the  Graneros  shale,  and  the  Pierre  shale 
furnish  suitable  raw  materials. 
NATURAL    CEMENT    ROCK 
A  calcareous  shale,  ra1  her  fissile  and  of  light-gray  color,  a  part  of  the 
Graneros  -hale,  i-  exposed  on  the  north  side  of  the  small  stream  that 
is  crossed  by  the  railroad  2\  mile-  southeast  of  Newcastle.  A  thicla 
ness  of  H»  feet  of  shale  is  exposed  on  a  small  whitish  hill  west  of  the 
railroad.  The  amount  of  gj  psum  in  I  his  -hale  is  too  small  to  interfere 
with  its  use  a-  a  Portland  cement  material,  [nterbedded  with  the 
shale,  20  feet  from  the  top  of  the  sampled  portion,  are  thin  beds  of 
limestone  one-half  inch  thick.  The  shale  occurs  here  in  considerably 
bodies,  which  could  probably  he  worked  with  a  -team  shovel.  The 
following  is  an  analysis  of  this  limy  -hale,  or  shaly  limestone,  as  it^ 
appear-  t«>  he.  made  by  Messrs.  Phillip-  and  Bates: 
Analysis  of  shale  from  i«>>ni  j\  miles  southeast  of  Newcastle. 
Silica    SiO.   L8   L0 
Alumina     \l_<>,  6.26 
Feme  oxide    Fe20         s<> 
Manganese  oxide    MnO) 50 
Lime    CaO      37.57 
Magnesia    MgO  7*i 
Sulphuric  anhydride    S03 27 
vlk.llles      fNa.0 2.14 
Alkjl' "  "-IK...) 92 
Water  at  L00°  C L.  25 
Ignition  loss 31.  58 
LOO.  L5 
This  highly  clayey  limestone  would  make  an  excellent  base  for  the 
manufacture  of  cement,  and  if  mixed  with  a  small  amount  of  pure 
