468  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
sand  is  light  green.  The  dark-brown  layers  arc  not  utilized,  but  the  fainter-colored  beds 
are  sometimes  worked  in  with  the  while  sand,  as  the  color  of  the  resulting  mixture  is  scarcely 
perceptible.  There  is  considerable  variation  in  the  hardness  of  the  sandstone.  Toward 
the  top  of  the  quarry  the  sand  is  loosest ,  as  it  has  little  or  no  cover.  Through  the  middle  of 
the  quarry  face,  along  bedding  planes,  run  certain  hard  crusts,  where  the  sand  has  been 
unusually  cemented.  This  cementation  occurs  in  the  whitest  sand,  which  otherwise  would 
be  most  desirable  to  work.  Segregations  of  quartzite,  termed  "niggerheads,"  also  occur. 
One  bed  of  light-brown  sand,  coarser  grained  than  the  average,  sparkles  in  the  sunlight,  as 
it  has  undergone  recrystallization.  This  sand  is  said  to  be  highly  desirable  for  rock  sawing, 
on  account  of  its  sharpness  and  coarseness.  The  sand  is  crushed,  dried,  and  screened  here. 
Cable  and  belt  conveyors  move  the  material,  and  drying  is  accomplished  by  steam  coils, 
through  which  the  sand  gradually  settles. 
The  quarries  of  the  Missouri  Silica  Company  arc  north  of  the  railroad  tracks,  about  three- 
fourths  of  a  mile  east  of  the  union  station  at  Pacific.  A  large  quantity  of  sand  has  been 
removed  from  the  bluff  here,  and  the  quarry  now  presents  a  face  75  feet  high  by  400  feet 
long,  capped  by  green  sandy  shale  and  overlying  limestone.  Near  the  top  the  sandstone  is 
of  a  greenish  color  and  is  cross-bedded.  At  this  quarry  the  sandstone  is  very  soft  and  friable, 
breaking  down  under  the  influence  of  a  heavy  rain.  This  condition  might  lender  possible 
the  hydrauiicking  of  the  deposit  in  a  manner  similar  to  t  hat  employed  at  Ottawa,  [11.,  par- 
ticularly since  a  large  pit  at  the  bottom  of  the  quarry  is  now  filled  with  water,  and  under 
present  condit  ions  is  a  hindrance  to  the  work.  The  best  grade  of  sand  is  obtained  from  the 
lower  pari  of  the  quarry,  and  is  used  for  the  liner  grades  of  glassware  and  plate  glass;  the 
second  grade,  used  for  window  glass  and  fine  bolt  les,  comes  from  the  middle  beds,  while  the 
upper  material  is  suitable  for  colored  bott  les  and  for  jars.  The  extent  to  which  this  deposit 
has  been  worked  brings  it  near  the  limit  of  profitable  st  ripping,  unless  new  methods  of  work- 
ing are  substituted  for  those  common  to  this  locality.  Some  sand  has  been  obtained  by 
excavating  caves  into  the  bin  If.  but  owing  to  the  looseness  of  the  sand  I  his  method  can  not 
be  depended  on  here  unless  the  sand  is  excavated  completely  up  to  I  lie  limestone  roof. 
The  first  quarry  east  of  the  union  station,  north  of  the  t  rack,  at  Pacific  is  operated  by  the 
Pacific  Glass  Sand  Company.  A  lace  of  some  60  feel  of  sand  is  being  blasted  down  here  and 
crushed,  washed,  dried,  and  screened  at  I  lie  mili.  The  sandstone  extends  below  the  quarry 
and  may  reach  a  total  thickness  of  100  feet.  The  variations  in  color  mentioned  above 
are  noticeable  here,  the  colored  sand  running  in  strips  and  pockets.  The  greater  part  of 
the  prepared  sand  from  this  plant  goes  to  the  works  of  I  he  St .  Louis  Plate  ( rlass  Company, 
at  Valley  Park,  Mo.  The  sand  is  subjected  to  two  washings,  which  remove  a  small  amount 
of  "sediment  ."  apparent  ly  a  very  fine  clay,  and  also  tend  to  reduce  t  he  color.  Even  after 
tiie  second  washing  the  sediment  forms  a  thin  dim  on  successive  layers  of  sand  in  (he  bins. 
The  resulting  color  of  the  prepared  sand  is  a.  very  light  yellow,  imperceptible  except  in 
large  masses.     Plate  glass  made  from  it  show    the  usual  pale-green  tint  on  broken  edges. 
Crystal  ( 'ity.  Forty  miles  south  of  St .  Louis,  on  the  Frisco  Railroad,  at  Crystal  City,  the 
plant  of  the  Pittsburg  Plate  Glass  Company  is  supplied  with  silica  from  its  sand  mines  at 
that  point.  The  St.  Peter  sandstone  lies  relatively  low  here,  and  only  the  upper  10  feel 
can  be  obtained  by  present  methods.  The  openings  are  on  the  east  side  of  a  small 
ravine  that  enters  Plattin  Creek  from  the  southeast.  The  sandstone  rises  about  30  feet 
above  the  floor  of  this  ravine.  It  is  overlain  by  thin  sandy  shale,  with  medium  beds  of  lime- 
stone above.  In  working  the  san  1  the  overlying  rock  was  first  stripped  back  as  far  as 
practicable,  or  until  a  thickness  of  about  15  feel  of  the  limestone  was  reached.  Tunneling 
into  the  sandstone  was  then  begun,  and  now  five  or  six  openings  enter  the  bluff  into  con- 
nect ing  chambers,  which  have  largely  been  mined  out  for  about  100  feet ,  with  the  except  ion 
of  the  pillars.  Other  tunnels  extend  in  i  ne-fourth  mile  farther,  and  considerable  sand  has 
been  removed  all  the  way  back.  The  floor  of  the  openings  is  about  5  i\c\  below  the  bottom 
of  the  ravine,  but  it  has  been  impossible  to  mine  much  below  this  level  on  account  of  ground 
water.     About  25  feet,  vertically,  of  sand  are  removed,  leaving  6  to  10  feel  as  roof.     The 
