GLASS    SAND    OF    MIDDLE    MISSISSIPPI    BASIN.  469 
sand  has  not  been  removed  entirely  to  the  top,  on  account  of  the  impurity  of  the  upper  beds, 
but  it  seems  that  the  overlying  limestone  might  make  a  good  roof  after  sonic  of  the  lower 
shaly  layers  are  pulled  down.  This  method  of  mining  is  reported  to  be  more  expensive 
than  open-pit  workings,  where  stripping  is  necessary  for  only  a  few  feet. 
The  sand  appears  in  general  rather  uniform  in  color,  but,  contains  a  lew  pale-yellowish 
streaks  and  is  a  trifle  coarser  than  that  from  the  quarries  farther  north.  Several  very 
white  streaks  near  the  top  are  somewhat  harder  than  the  rest,  hut  as  the  ground  level  is 
approached  the  rock  becomes  more  and  more  friable  The  product  for  melting  is  crushed 
washed,  and  dried.  An  appreciable  yellow  sediment  is  removed  by  washing.  Crushed 
but  not  washed  sand  is  used  in  the  factory  for  grinding  and  beveling  plate  glass.  In  this 
process  the  sand  grains  are  made  finer  and  finer,  and  the  various  grades  are  used  succes- 
sively, being  finally  replaced  by  emery  powder  and  rouge  in  polishing.  The  quantity  of 
sand  in  sight  that  may  be  won  by  the  present  process  should  be  sufficient  to  supply  the 
factory,  with  its  proposed  enlargements,  for  several  years,  since  on  the  opposite  side  of  the 
ravine  little  has  been  removed  except  from  the  tunnel  through  which  the  railroad  spur 
reaches  the  mine.  No  sand  is  at  present  being  shipped  from  here,  however,  presumably 
because  of  the  cost  of  production.  The  friable  condition  of  the  sand  below  water  level  sug- 
gests that  much  of  this  material  might  be  obtained  by  pumping  it  up  into  the  mill. 
Silica. — At  this  place  also,  32  miles  south  of  St.  Louis,  on  the  St.  Louis,  Iron  Mountain 
and  Southern  Railway,  is  a  large  sand  quarry  in  the  St. Peter  sandstone,  where  beds  lower 
than  those  at  Crystal  City  are  reported  to  be  worked. 
UNDEVELOPED   RESOURCES. 
The  St.  Peter  sandstone,  the  formation  furnishing  all  the  materia]  now  being  exploited 
in  the  area  here  considered,  has  a  very  wide  extent.  It  outcrops  in  the  Mississippi  Valley 
in  the  States  of  Minnesota,  Wisconsin,  Iowa,  Illinois,  and  Missouri,  and  also  around  the 
flanks  of  the  Ozark  uplift  in  Missouri,  Arkansas,  and  Indian  Territory.  Wherever  it  has 
been  recognized  it  usually  presents  the  same  characteristics,  viz,  massive  beds  of  very 
friable  sandstone,  having  a  total  thickness  ranging  from  25  to  possibly  300  feet,  com- 
posed almost  entirely  of  well-rounded,  translucent  quartz  grains  of  slight  variation  in  size. 
These  features,  so  persistent  throughout  its  extent,'  render  it  of  value  as  a  glass  sand. 
Consequently,  wherever  this  rock  occurs  it  may  contain  the  substance  at  least  of  a  glass 
sand.  Locally  the  sandstone  has  been  observed  to  be  badly  iron  stained,  also  indurated 
to  quartzite,  both  of  which  conditions  render  it  of  little  value  for  glass  making  in  compar- 
ison with  the  abundant  unchanged  material.  In  northern  Arkansas  the  St.  Peter  formation 
has  been  found  to  contain  a  lens  of  dolomite,  but  even  under  this  circumstance  either  or 
both  the  overlying  and  the  underlying  phases  of  sandstone  maybe  of  workable  thickness. 
Aside  from  the  St.  Peter,  there  are  other  formations  in  this  region  containing  beds  of  sand 
that,  under  certain  conditions,  may  prove  of  value  as  glass  material.  Chief  among  these 
are  Ordovician  sandstones,  older  than  the  St.  Peter,  the  Devonian  and  Carboniferous  sand- 
stones present  in  northwestern  Arkansas  and  southwestern  Missouri,  the  Buxton  for- 
mation in  the  Independence  and  Fredonia  quadrangles  in  southeastern  Kansas,  and  the 
"Potsdam"  or  "Jordan"  sandstone  in  the  Wisconsin  and  Mississippi  valleys  in  Wisconsin 
and  adjoining  portions  of  Iowa. 
MISSOURI. 
Southeast  of  Crystal  City  there  is  a  good  development  of  St.  IYfer  sandstone,  in  Sic. 
Genevieve  County,  and  at  Jackson,  Cape  Girardeau  County,  the  sand  has  been  quarried. 
Samples  from  Jackson  submitted  to  the  office  of  the  Survey  are  rather  line  grained  and 
friable  and  contain  a  small  proportion  of  sharp  or  subangular  grains.  Some  of  the  mate- 
rial is  iron  stained,  and  these  portions  are  rather  firmly  cemented.  (See  item  No.  12  in 
tables  on  pp.  462-463  for  properties.)  Chemically  this  sand  is  well  qualified  for  glass 
making,  and  while  the  sample  submitted  comes  near  the  limit  of  fineness,  screening  would 
doubtless  render  it  highly  satisfactory. 
