300         CONTRIBUTIONS    TO   ECONOMIC    GEOLOGY,  1006,  PART    I. 
converters  in  the  smelting  process,  a  use  to  which  it  is  well  adapted. 
An  analysis  of  this  clay  is  as  follows: 
Analysis  of  clay  from  the  chirk  mine,  Clarhville,   \.  Mex. 
Silica  (Si02) 64.73 
In. ii  oxide  i  IVOi 6.53 
Aluminum  oxide  I  A.l203) 17.75 
Volatile  matter 5.09 
Water 4.36 
It  will  be  noticed  that  the  content  of  fusible  material,  principally 
iron  oxide,  is  rather  high  for  a  fire  clay,  but  the  presence  of  this 
impurity  does  not  seem  to  he  detrimental  to  its  use  as  converter- 
iining  material.  Many  of  the  copper  ores  themselves  contain  a  high 
percentage  of  iron,  hence  that  present  in  the  converter  lining,  if  in 
rather  small  quantity,  does  not  add  greatly  to  the  total  percentage. 
It  must  he  home  in  mind,  too,  that  the  linings  of  copper  converters 
are  renewed  before  nearly  every  charge  of  ore,  so  that  a.  lining  of 
absolute  refractory  character  is  unnecessary.  Quart zite  is  some-  I 
times  mixed  with  the  clays  used  for  this  purpose,  with  the  effect  of 
greatly  reducing  the  relative  percentage  of  iron  in  the  lining. 
Besides  tin's  production,  which  in  itself  amounts  to  nearly  30, 000    ; 
tons  annually,  Valued  on  the  cars  at  the  <piarries  and  mines  at  about  I 
$1.15   per   ton.    some   building   brick   have   been   successfully  made  ] 
from  the  Mancos  -hale  that  outcrops  in  the  "Hogback"  2  miles  east 
of  Gallup.     The  production  of  these  brick  has  been  limited  by  the  I 
local  demand,  and  none  have  been  produced  for  several  years.     As  1 
is  shown  by  the  following  analysis  made  by  Prof.  Erasmus  Flaworth, 
of  Kansas  State  University,  this  shale  is  not  an  exceptionally  good 
brick  shale,  being  rather  high  in  lime.     The  presence  of  this,  how- 
ever, would  not   he  detrimental  if  the  shale  were  comparatively  free 
from  carbonaceous  matter,  hut   unfortunately  its  carbonaceous  con- 
tent  is  rather  large,  the  ignition  loss,  probably  in  great   part  organic 
matter,  being  some^  hat  high. 
Inalysis  of  \lnn<<>s  shalefrom  Hogback  east  of  Gallup. 
Si02 56.  29 
l-V.<  )  ■   U20 23.  18 
CaO 3.73 
Mg<  I 2.  01  * 
Loss  "ii  ignition 11.  53 
It  is  possible  that  this  shale  bed  or  other  beds  in  the  overlying 
Mesaverde  formation  might  be  utilized,  with  some  of  the  limestones 
occurring  southeast  and  east  of  Gallup,  in  the  manufacture  of  Port- 
land cement.  No  analyses  of  these  limestones  have  yet  been  made, 
however,  so  that  a  definite  statement  as  to  their  quality  is  at  present 
impossible. 
