CLAYS  AM)  (LAV  PRODLCTS. 
PROPERTIES  AM)   TESTS  OF  FULLER'S  EARTH.1 
By  John  T.  P 
GEOLOGY   AND   ORIGIN. 
Practically  all  workable  deposits  of  Fuller's  earth  are  of  secondary 
origin,    having    been    redeposited    in    sedimentary    series.     Residual 
deposits  are  also  known.  For  example,  in  Saxony,  where  tin*  fuller's 
earth  is  found  in  situ  derived  From  gabbro.  As  is  to  be  expected 
from  its  origin,  the  deposits  an1  most  frequently  found  in  the  Tertiary! 
Formations.  Thus  the  well-known  beds  at  Quincy,  Fla.,  are  of  the 
Miocene  epoch,  and  the  earths  in  South  Carolina  belong  to  the  Eoeene 
and  Neocene  format  ions.  The  extensive  deposits  of  South  Dakota  are 
also  of  Tertiary  age,  hut  in  which  division  1  am  unable  to  state.  On 
the  other  hand,  certain  British  deposits  are  stated6  to  belong  to  the 
lower  greensand  (Lower  Cretaceous),  and  Dana''  mentions  the 
"  fuller-  earth  group"  a-  a  subdivision  in  oolite  of  t  he  Jurassic  period. 
Gabbro,  diorite,  diabase,  and  basalt  are  mentioned  by  different 
writers  a-  rock-.  From  which  fuller's  earth  is  derived.  It  will  be 
noticed  that  these  rocks  are  all  similar  in  their  nature  and  belong 
to  either  the  hornhlendic  or  basaltic  series.  Their  characteristic 
mineral  constituents  are  the  augites  and  hornblendes,  with  the  feld- 
spars less  prominent  :  the  zeolites  magnetite,  ilmenite,  olivine,  and  other 
minerals  ma\  also  he  present.  The  subjoined  table  e;i\es  a  list  of 
minerals  which  from  lithologic  considerations  would  seem  likely  to 
he  found  in  Fuller's  earth.  This  li>t  embraces  not  only  the  above- 
mentioned  minerals,  hut  also  the  hydrous  aluminum  silicates  or  clay 
minerals  which  may  result  from  their  decomposition.  For  con- 
venience in  reference,  the  chemical  composition  and  certain  physical 
properties  are  also  tabulated. 
q  Tin'  work  on  which  this  report  is  based  was  carried  out  in  the  laboratory  and  at  the  expense  of 
Mr.  Charles  Catlett,  of  Staunton,  Va.,  in  connection  with  an  investigation  <>f  the  subject  for  private 
persons.  Mr.  Catletl  lias  kindly  placed  the  results  of  this  work  at  die  disposal  of  the  Survey,  and 
as  they  seem  to  represenl  the  first  detailed  series  of  comparative  tests  on  such  materials  it  has  been 
decided  to  publish  them  in  the  present  bulletin.     E.  C.  E. 
b  Nineteenth  Ann.  Rept.  I  .  S   Geol.  Survey,  pt.  6,  continued,  1898,  p.  408. 
•  Dana,  J.  D.,  Manual  of  Geology,  1895,  p.  77.",. 
268 
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