ABRASIVE  MATERIALS 
DIATOMACEOUS     DEPOSITS    OF    NORTHERN 
SANTA    BARBARA  COUNTY,  CAL. 
I:     l:  \i  rn   Aknoi  n  and    Robi  r  i     \  ndi 
INTRODUCTION. 
I  >uring  the  summer  of  L906  the  writers,  with  the  assistance  of  II.  K. 
Johnson,  made  a  more  or  less  detailed  survey  of  the  Lompoc  and 
Guadalupe  quadrangles,  California,  embracing  the  Santa  Maria  oil 
field  of  northern  Santa  Barbara  County,  to  determine  the  area!  dis- 
tribution and  structure  of  the  oil-bearing  formations  within  their 
boundaries.0  The  diatomaceous  deposits  thai  were  examined  during 
the  courseof  the  investigations  occui  in  such  practically  inexhaust- 
ible quantities  in  proximity  to  railroad  and  ocean  transportation 
facilities  thai  thej  were  deemed  worthy  of  description  in  this 
bullel  in. 
Although  these  deposits  have  been  known  locally  for  a  long  time 
and  have  received  brief  notice  in  such  publications  as  Mineral 
Resources  "I"  the  United  States  and  in  the  reports  of  the  California 
St  .-lie  Mining  Bureau,6  yel  there  is  a  general  lack  of  knowledge  in 
regard  to  their  importance,  as  is  shown  by  the  absence  of  any  mention 
of  them  in  tin-  standard  text-books,  where  much  smaller  deposits  are 
emphasized. 
[nfusorial  earth,  tripoli,  or  diatomaceous  earth,  as  the  same  mate- 
rial is  variously  called,  is  of  widespread  occurrence  in  the  California 
coast  ranges  and  is  found  unaltered  in  great  abundance  in  northern 
Santa  Barbara  County,  where  it  is  usually  known  by  the  name  of 
diatomaceous  earth  or  "chalk  rock."  The  former  designation  is  a 
very  proper  one  to  apply,  as  the  formation  is  almost  entirely  made 
up  of  the  skeletons  of  minute  organisms  called  diatoms.     These  are 
a  a  preliminary  report  by  the  writers  on  the  geology  and  oil  occurrence  in  this  region  is  being  pub 
Lished  by  the  United  States  Geological  Survey  as  Bulletin  No.  317. 
b  For  a  brief  account  of  tin ■  various  diatomaceous  deposits  of  California  see  The  structural  and  indus- 
trial materials  of  California:  Bull.  California  State  Min.  Bur.  No.  38, 1906,  pp.  289-2 
438 
