MAGNESITE    DEPOSITS    OF    CALIFORNIA.  389 
were  coated  with  lampblack.  A  small  amount  of  chromite  has  been  found  in  the  neighbor- 
hood, but  not  in  paying  quantities.  An  analysis  of  magnesite  from  this  mine  is  given  on 
the  next  page. 
POPE    VALLEY. 
What  is  usually  known  as  the  Wallers  magnesite  mine  is  located  on  the  easl  side  of  Pope 
Valley,  22  miles  northeast  of  Rutherford.  The  distance  of  the  mine  from  the  railroad  makes 
hauling  expensive,  and  the  mine  has  never  been  worked  on  a  huge  scale  and  has  had  no  pro- 
duction for  several  years.  A  proposed  electric  road  from  San  Francisco  to  Lake  County  will 
pass,  if  built,  within  4  miles  or  less  of  the  mine,  in  which  case  it  will  be  in  an  excellent  position 
to  ship  magnesite. 
The  deposits  are  situated  in  a  serpentine  hill,  about  400  feet  (barometric  measurement) 
above  the  valley.  They  are  composed  of  a  large  number  of  veins  whose  exposures  vary  in 
width  from  a  fraction  of  an  inch  to  12  feet,  and  lie  on  both  sides  of  a  small  ravine  which 
forms  an  amphitheater,  with  an  easy,  straight  southward  grade  to  the  valley,  making  an 
almost  ideal  place  to  work  with  an  aerial  tram. 
The  deposits  are  in  three  principal  groups,  two  of  which  lie  on  the  east  side  of  the  ravine 
and  the  other  on  the  west.  In  the  main  group  on  the  east  side  are  three  large  veins  of 
magnesite  which  can  be  definitely  traced  for  distances  of  about  140,  250,  and  230  feet 
respectively,  with  strikes  of  N.  28°,  30°,  and  45°  W.  At  their  north  end  the  western  and 
eastern  veins  are  but  30  feet  apart,  with  the  middle  vein  probably  converging  with  the 
eastern  one.  The  dip  of  the  western  vein  is  shown  by  a  shallow  shaft  to  be  50°  E.  The 
veins  stand  up  boldly  and  can  be  seen  from  any  part  of  the  valley  not  hidden  by  hills. 
Longitudinal  faults  occur  in  both  of  the  outer  veins.  Between  the  large  ones  are  many 
smaller  veins  having  a  general  parallelism  to  the  main  bodies.  At  its  widest  exposure 
the  western  vein  is  about  10  feet  thick,  of  which  about  5  feet  on  the  foot  wall  are  solid 
white  magnesite,  while  the  upper  5  feet  (on  the  hanging-wall  side)  contain  many  inclusions 
of  serpentine.  The  structure  of  the  eastern  vein  is  similar  and  in  places  the  magnesite 
may  be  seen  grading  into  the  country  rock.  It  is  about  12  feet  wide  where  exposed  in  a 
shallow  crosscut.  In  the  middle  vein  a  width  of  IS  inches  to  5  feet  of  clear  white  magnesite 
is  exposed. 
There  has  been  some  crushing  of  the  magnesite  and  the  broken  particles  have  been 
cemented  with  yellowish,  less  pure  material.  Part  of  the  magnesite  has  formed  in  yellowish 
botryoidal  masses  that  are  rather  impure.  Some  crystalline  magnesite,  similar  to  that  of 
Chiles  Valley,  is  found  in  the  crevices.  But  a  small  amount  has  been  mined,  and  that  was 
simply  broken  from  the  exposed  faces  of  the  veins. 
A  second  group  of  veins  with  a  more  northerly  strike  occurs  100  feet  or  more  above  the 
veins  just  described.  The  veins  forming  this  second  group  are  smaller,  running  from  2 
inches  to  2  feet  in  width,  and  the  larger  ones  are  impure.  There  are  also  many  scattered 
veins  in  the  intervening  space. 
On  the  west  side  of  the  ravine  is  a  third  group  of  veins  200  to  250  feet  from  those  first 
described,  with  a  strike  between  north  and  northwest.  The  largest  is  a  vein  4  to  6  feet 
wide  and  seven  others  from  1  to  2  feet  wide  occur  within  a  space  of  125  feet.  All  are  of 
excellent  quality.  It  would  seem  possible  to  blast  out  the  whole  of  the  rock  through 
this  distance  and  hand  pick  it,  should  the  deposits  again  be  worked. 
PORTERVILLE    DEPOSITS. 
The  Willamette  Pulp  and  Paper  Company  is  working  a  large  group  of  magnesite  veins 
4  miles  northeast  of  Porterville,  in  the  outer  range  of  foothills  of  the  Sierra  Nevada.  The 
veins  occur  in  a  brown  serpentine,  derived  from  peridotite  and  having  an  apparent  bedding 
structure.  The  serpentine  forms  part  of  a  metamorphic  complex  of  amphibolite-schist, 
serpentine,  and  other  magnesian  rocks,  some  talcose  and  mica  bearing,  and  a  small  amount 
of  fine-grained  quartzite.  The  rocks  have  a  general  northerly  strike,  with  a  high  (00°) 
easterly  dip.  They  are  cut  off  by  a  granitic  mass  on  the  south,  a  I'ew  hundred  feet  from 
the  deposits,  and  several  granitic  dikes  cut  the  serpentine  and  other  rocks.     Basic  dikes 
