224 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
than  4  foot  in  thickness, 
exploited  area,  however, 
The  bed  is  said  to  extend  lor  at  least  2\  miles  along  the  strike,  the 
being  only  some  3,000  or  4,000  feel  long.  The  roof  is  of  sandstone, 
while  the  floor  is  clay,  made  up  of  de- 
composed serpentine  and  other  Francis- 
can rocks.  Whether  or  not  this  clay 
represents  the  residuum  from  prc-Mioccne 
surface  decomposition  oris  finely  groum 
material  along  a  fault  /.one,  the  writer  is 
not  prepared  to  state. 
Properties  of  the  coal. a  The  coal  is  hard 
and  exhibits  a  clean  black  fracture.  Al-  . 
though  called  a  lignite,  ii  appears  to  al 
proach  bituminous.  It  carries  no  iron 
pyrites,  the  large  quantity  of  contained 
sulphur  occurring  principally,  so  it  is  said,  J 
in  the  form  of  calcium  sulphate.  The  coal 
does  not  take  lire  spontaneously  and  is 
noncoking.  Heating  tests  show  its  ca]B 
rifle  power  to  he  13,000  British  thermal 
units.  The  following  analyses,  taken  froH 
a  mining  engineer's  report  on  the  mine. 
.'  ii  are  said  to  represent  fair  averages  from 
different  parts  of  the  mine: 
■    p 
P    - 
o   o 
-.  - 
inalyses  of  coal  from  Stone  Canyon  mine. 
Sample 
from 
w  ater. 
Volatile 
carl, on. 
Fixed 
carbon. 
Ash. 
P.ct. 
/'.  r/. 
P.  Cl. 
P.ct. 
Tunnel 
(•.  l  :>, 
50.08 
36.39 
7.40 
Do. 
ii.  ll 
48.57 
38.84 
6.51 
Do. 
5.50 
50.34 
37.61 
6.  55 
DO. 
7.  12 
49.15 
34.88 
8.93 
Shaft.. 
4.80 
51.40 
34.21 
1.0.59 
Do. 
4.42 
46.  30 
30.  54 
18.71 
Do. 
3.82 
53.28 
38.35 
1.  55 
Do. 
2.99 
53.38 
38.28 
5.  38 
Sul- 
phur. 
4.8S 
;,.(« 
4.74 
0.41 
5.  7< 
4.8* 
5.  d 
Conclusions. — The  coal  appears  to  have 
been  formed  in  a  basin  previous  to  the 
principal  MioGene  subsidence.    The  limits 
of  this  basin  are  unknown,  although  a  de- 
posit of  coal  found  near  La  Pan/a,  nearly 
50  miles  southeast ,  and  occupying  a  simi- 
lar stratigraphic  position  to  that  of  the 
Stone<  'atiyon  bed  offers  evidence  of  rat  he! 
widespread  coal-forming  conditions  at  1  lit 
beginning  of  the  Miocene. 
Considerable  prospecting  has  been  carried  on  along  the  top  of  the  range  al  the  contact 
between  the  Santa  Margarita  sandstone  and  the  Franciscan  rocks,  in  an  apparently  analcj 
Lrou>  position  stratigraphically  to  that  in  which  the  coal  occurs  on  the  west  side  of  the  synclinJ 
a  The  t\ riter  is  indebted  to  Mr.  M.  J.  Horswell,  assistant  superintendent  <>f  t lie  Stone  Canj en  coffl 
mine,  for  a  large  part  of  the  following  information  concerning  the  physical  and  chemical  propertii  <■] 
the  coal. 
