556  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
hibits  the  iron  minerals  in  varying  stages  of  decomposition  and 
oxidation.  The  transported  or  washed  clay  is  pure  white  in  appear- 
ance, and  has  been  derived  chiefly  from  the  feldspars  of  the  granite 
and  pegmatite  dikes.  This  clay  is  very  fine  grained  and  free  from 
grit.  It  has  a  greasy  feel,  is  plastic,  and  in  water  slakes  quickly. 
The  clays  at  Mica  are  used  chiefly  by  the  American  Fire  Brick 
Company  in  the  manufacture  of  sewer  pipe  and  fire  brick. 
Between  Mica  and  Spokane,  especially  in  the  neighborhood  of 
Chester,,  are  deposits  of  clay  similar  in  appearance,  character,  and 
origin  to  those  of  Mica.  At  a  few  points  some  test  pits  have  been 
dug  in  them,  but  for  the  most  part  they  are  wholly  undeveloped.  A 
company  has  lately  begun  the  manufacture  of  clay  goods  at  Chester, 
and  it  is  likely  that  similar  industries  will  soon  be  established  at 
near-b}^  places. 
About  3  miles  from  the  center  of  Spokane,  along  Latah  Creek, 
is  a  deposit  of  clay  which  has  been  used  in  making  common  bricks. 
The  clay  varies  in  color  from  an  almost  pure  white  to  buff  or  brown, 
with  occasional  streaks  of  an  orange  hue.  It  is  usually  massive, 
but  often  shows  a  fine  lamination.  It  breaks  with  a  conchoidal  frac- 
ture and  with  sharp  edges.  It  is  fine  grained,  possesses  a  gritty  feel, 
and  lias  all  through  it  very  small  flakes  of  muscovite  mica.  The 
clay  has  evidently  been  derived  from  a  granitoid  rock,  although 
basalt  is  the  only  country  rock  in  the  immediate  neighborhood.  A 
casual  inspection  of  the  deposit  failed  to  bring  to  light  the  origin  of 
the  clay.  Elsewhere  about  Spokane,  between  extrusive  sheets  of 
basalt  there  are  beds  of  clay  of  lacustrine  origin.  The  clay  in  ques- 
tion may  represent  such  a  deposit  with  the  basalt  removed  from  above 
it,  or  it  may  be  a  part  of  the  extensive  deposits  of  glacial  origin 
which  line  the  valley  of  Spokane-  River  throughout  almost  its  entire 
length. 
At  Clayton  there  are  extensive  deposits  of  clays  which  have  been 
utilized  for  a  number  of  years.  They  are  used  chiefly  by  the  Wash- 
ington Brick,  Lime,  and  Manufacturing  Company  in  the  manufac- 
ture of  terra  cotta,  pressed,  vetrified,  sidewalk,  and  common  bricks, 
fire  proofing,  roof  tiles,  drain  tiles,  and  sewer  pipe.  The  clay  is 
also  used  by  the  Standard  Stoneware  Company  in  the  manufacture 
of  stoneware  and  flower  pots.  The  clay  deposits  are  located  upon 
an  extensive  plain,  almost  level  or  gently  rolling,  and  from  test  pits 
and  drill  holes  they  are  known  to  cover  several  thousand  acres.  The 
beds  lie  almost  flat  and  are  usually  covered  by  only  a  thin  coating 
of  soil.  Some  of  the  clay  is  clearly  of  residual  origin,  being  derived 
from  the  decomposition  of  granite,  which  is  the  bed  rock  of  Clayton 
and  vicinity.  The  clay,  or  more  properly  sand,  thus  produced  varies 
in  color  from  white  to  red.  The  feldspar  has  been  changed  to 
kaolinite;    the  quartz  has  been  set  free,  and  the  iron-bearing  niin- 
