390 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   L905. 
of  several  varieties  cut  both  the  country  rock  and  the  veins  and  arc  occasionally  squeeze  ;i 
to  a  schist. 
Faulting  is  frequent,  but  the  serpentine  is  not  divided  into  the  small  irregular  block  , 
usual  in  the  Coast    Range  and  many  other  serpentines,  due  to  the  swelling  of  the  rock  as  i 
changes  its  chemical  form.      Internal  movement  is  evident  and  the  magnesite  is  invariabl;  j 
crushed  in  the  larger  veins.      In  one  vertical  2-foot   vein  a  couple  of  hundred  feet  southeas  -] 
of  the  kiln  the  magnesite  has  been  so  squeezed   that  it  has  taken  a  modified  cone-in-cont  J 
structure  and  i-  left   in  irregular  fragments  whose  sides  are  covered  with  abrasion  lines 
the  whole  looking  as  if  at  the  time  of  crushing  it  had  been  in  a  semiplastic  state.     In  othej  \\ 
veins  the  planes  along  which  the  magnesite  has  moved  on  itself  are  smooth  and  shape* 
so  as  to  somewhat  resemble  the  curve  of  a  highly  arched  shell.     Along  these  planes  is  oftei 
a  bright-red  stain  of  iron  oxide,  although  the  surrounding  magnesite  is  pure  white.     At 
the  north  end  of  the  deposits  are  several  "blanket  "  or  Hat  veins.     The  largest  one  is  prac- 
tically   horizontal   in   the   middle   part    and  somewhat    uptilted   at    both   ends.      It    extends 
through  the  hill  a  distance  of  362  feet,  and  is  probably  twice  as  long,  and  from  '2  to  I  or 
re  feel  thick.     A  basic  dike  flattens  and  spreads  under  a  huge  part  of  the  vein  in  a  thin 
sheet    1    to  2  feet    thick;   then,   breaking  through,   it    overlies  the   remainder  of  the   vein. 
There  is  nothing  to  -how  that  the  vein  has  been  tilted  from  a  more  upright  position  to 
it-  present  place  and  it  was  evidently  formed  a-  it  lies.  Hat  and  cutting  across  the  verticd 
structure  of  the  serpentine.  This  is  accounted  for  l»\  supposing  that  there  was  a  slow 
movement  in  the  rocks  along  this  plane  :ii  the  time  of  the  vein's  deposition,  the  magnesite 
filling  uneven,  open  spaces  along  the  horizontal  fault,  and  that  when  there  was  another 
movement  these  depositions  would  hold  the  ma--  apart  and  make  room  for  contiguous 
deposits.  The  crushed  condition  of  the  whole  mass  and  inclusions  of  serpentine  in  lines 
approximately  parallel  to  the  sides  of  the  vein  give  this  hypothesis  some  color.  The  other 
"blanket"  veins  lie  at  rather  low  angles  mid  will  probably  be  found  to  run  into  this  one. 
At  the  north  end  of  the  deposits  i-  a  stockwork  of  small  veins  2  to  6  inches  thick,  and  it  is  - 
thought   that   it   ma\    pay  to  blast    the  whole  mass  and  hand  pick  it. 
With  the  exception  of  magnesite  shipped  to  t  he  We- tern  Carbonic  Acid  Gas  Company,  of 
San  Francisco,  for  making  gas,  all  t  he  magnesite  mined  here  i-  burned  before  being  shipped 
Crude  oil  is  used  for  fuel,  and  the  magnesite  i-  led  into  the  top  of  a  kiln,  gradually  rising 
in  temperature  until  it  reaches  the  flame  from  the  burners.  It  i-  then  raised  to  a  white 
heat  and  kept  there  for  from  twenty  lo  twenty-live  minute-,  when  it  is  withdrawn.  Ship- 
ment- are  made  from  llilo,  a  spur  on  the  Southern  Pacific  Railroad,  I  mile  north  of 
Porterville. 
Analyses  ofmagnesiU  <in<l  magnesia. 
1. 
2. 
3. 
4. 
5. 
0. 
7. 
8. 
Silica  (Si02) 
0.  in 
.25 
0.50 
.30 
1.  in 
.47 
.70 
'.•7.  35 
3.30 
7.  25 
.84 
2   18 
84.72 
2.48 
6.02 
1.  18 
4.34 
84.  50 
«1.81 
.08 
Trace. 
a  6.  68 
15.  to 
"  o.  98 
tron  oxide  -  Fes  O3) 
Alumina  1  AI2O3) 
.  49 
Lime  (Ca<  1 
.62 
47.10 
51.98 
.70 
n,  90 
51. 60 
l .  49 
Magnesia  1  M 
16.55 
51.25 
.  32 
37.23 
40.98 
44.39 
Carbon  dioxide  (CO 
50.06 
Water  a  ad  undetermined . .. 
1.  in 
!.:;.; 
2.  :>7 
100.05 
100.00      100.00 
99.99 
99.91 
inn.nn       99.99 
99.90 
"Insoluble. 
1,  2.  Alameda  claim,  American  Magnesite  Company,  :;■_'  miles  southeasl  of  Livermore,  Cal. 
3-.r>.  Same,  calcined. 
o.  chiles  Valley. 
7.  Same,  poor;  not  shipped. 
8.  Porterville. 
Analyst,  No--.  L-5,  unknown;  6-8,  Abbot  A.  Banks,  •">:;!  California  street,  San  Francisco,  Cal.,  <>et< 
ber  1, 1903. 
