340         CONTRIBUTIONS   TO   ECONOMIC    GEOLOGY,  1906,  PART    I. 
Analyses  of  air-dried  samples  of  flint  clay  from  C.  B.  McQueenfarm,  < 'Union  County,  I'a. 
I   LTIMATE    A.NALYSES. 
Silica  (Si02) 
Alumina  (Al203) 
Ferric  oxide  (Fe203 ) 
Manganese  oxide  (MnO). . . 
Lime  (CaO) 
Magnesia  (MgO) 
Sulphuric  anhydride  (S03) 
Soda(Na.O) 
Potash  (K20) 
Water  al  L00°  C 
Ignition  loss 
A. 
58.96 
56.  46 
25.  60 
27.  69 
3.32 
2.  51 
.07 
.()<> 
.70 
.12 
.25 
.28 
.07 
.14 
.  ir, 
.(Hi 
.36 
.  52 
.80 
1.   10 
9.90 
10.  01 
100    is 
B. 
LOO.  21 
i;  \T1<>\  \l      •.  NALYSES. 
Free  silica 
<  'lay  substance 
Feldspathic  substanc< 
Ignition  loss 
The  samples  thus  analyzed  wore  taken  from  a  3-foot  section  in  a 
now  drift  made  by  the  Sligo  Fire  Brick  Company.  Sample  A  repre- 
sents the  upper  1  foot,  and  sample  B  the  lower  2  feel  of  the  section. 
Sample  A  is  siliceous  in  appearance,  shows  ;t  rough  surface,  and: 
breaks  irregularly  rather  than  with  the  conchoidal  or  shell-like  frac- 
ture that  is  characteristic  of  (liul  clay.  Sample  B  is  like  the  type  of 
best  clay  described  above  except  that  instead  of  being  homogeneous 
it  contains  a  small  percentage  of  bluish  inclusions.  In  souk-  places  it 
shows  streaks  that  resemble  bedding  planes.  Wherever  cracks  occur 
in  the  clay  the  surfaces  formed  by  them  are  strongly  stained  with 
iron.  The  high  percentage  of  iron  shown  by  the  analyses  makes  a 
good  deal  of  the  day  unsuitable  for  use  in  the  manufacture  of  refrac- 
tory materials.  The  clay  in  the  bank  from  which  the  samples  were 
taken  for  analysis  is  used  by  the  Sligo  Fire  Brick  Company  in  the 
manufacture  of  fire  brick.  Clay  taken  from  below  the  Brookville(  0 
coal  in  the  mine  of  the  Sligo  Coal  and  Coke  Company  is  used  as  a 
bond.  The  bricks  are  sold  principally  for  use  in  open-hearth  fur- 
naces. The  reported  criticism  of  hricks  made  from  this  clay  is  that 
while  they  will  stand  relatively  high  temperatures  they  are  deficient 
in  resistance  to  friction. 
The  quality  of  the  clay  varies  from  place  to  place.     The  clay  south 
of  Clarion  River  appears  to  be,  on  the  whole,  better  than  that  north 
