116  CONTRIBUTIONS    TO   ECONOMIC    GEOLOGY,  1906,  PART    1. 
I  he  aspect  of  surface  deposits,  being  mere  coatings  or  films  of  an  appar- 
ent lv  secondary  mineral  in  joints  and  fractures  of  the  country  rock 
and  this  observation  is  corroborated  by  a  closer  examination  of  the 
ore  itself.  Under  the  microscope  thin  sections  of  material  from  the 
Caywood  No.  1  claim  show  the  cellular  structure  of  the  silicified  wood,: 
but  no  trace  of  impregnation  with  mineral  within  its  mass,  most  of 
the  carnotite  with  which  the  specimen  had  been  coated  having  been 
lost  in  the  grinding  of  the  thin  section.  Evidently  the  silicificat ion 
of  the  wood  was  fully  completed  before  the  carnotite  was  introduced. 
The  hand  specimen  shows  the  same  evidence,  only  the  outer  surface 
and  coarser  fractures  of  the  comparatively  impervious  wood  appearing 
to  contain  the  yellow  pigment. 
It  thus  seems  likely  that  carnotite  is  a  surf  ace  or  alteration  product, 
representing  in  a  secondary  form  some  other  original  minerals  from 
which  its  substance  has  been  derived.  As  it  has  probably  been 
deposited  from  solution  in  ground  water  it  is  very  likely  that  the 
source  of  the  rare  elements  which  the  deposits  contain  may  have  been 
at  some  considerable  distance,  and  it  is  possible  that  the  primary 
minerals  were  widely  disseminated  in  minute  quantities,  of  which  the 
present  deposits  are  a  product  of  concentration. 
Doctor  Ilillebrand  suggests  in  a  personal  communication  that — 
t  m;i1  ls  a  possible  source  of  the  vanadium  and  perhaps  uranium  in  carnotite  and  other 
evidently  secondary  minerals  thai  contain  one  or  the  other  of  these  elements.  This; 
suggest  i"ii  i-  haH'il  on  the  repeated  finding  of  vanadium  in  coal  ashes  and  the  observa 
tion  of  ii rani i mi  in  anthraeitie  bitumen  in  Sweden  and  in  nodular  forms  of  carbon  from 
the  oldesl  sedimentaries  of  thai  country,0  In  grahamite  from  "North  America,"  "  and 
in  carbonaceous  material  from  a  pegmatite  dike  in  Quebec. 6  Further,  in  the  San  Ra- 
fael Swell,  in  the  eastern  pari  of  Utah,  vanadium  has  been  found  l>\  me  in  relatively 
imounl  in  the  carbonaceous  material  accompanying  and  impregnating  sandstone, 
and  at  Cerro  do  Pasco,  rein,  carbonaceous  matter  very  rich  in  vanadium  occursJ 
These  facts  are  so  indicative  of  a  relation  between  vanadium  and  possibly  uranium! 
and  certain  coals  ami  carbonaceous  materials  that  an  examination  of  the  coals  and  bitta 
mens  of  western  Colorado  and  eastern  Utah  for  a  possible  contenl  in  these  elements 
seems  desirable.     If  found  in  them,  the  question  of  nil  i  mate  origin  won  Id  si  ill  remain. 
In  t  lis  connection  it  may  he  pointed  out  that  in  all  probability  the 
coal  seams  formerly  extended  over  and  far  beyond  the  position  of  the 
presenl  uranium  deposits;  that  these  strata  have  since  been  removed) 
by  erosion;  and  also  that  the  coal  seams  of  the  vicinity  are  at  present1 
largely  burned  along  their  outcrop.  On  the  other  hand,  it  seems  that 
had  these  rare  elements  been  derived  from  the  coal  seams  we  should 
now  find  t  races  of  minerals  containing  these  elements  among  the  sand- 
stones of  the  coal-bearing  strata,  rather  than  in  deposits  separated 
from  the  coal  beds  by  a  thickness  of  approximately  a  mile  and  a  half 
a  Nordenskiold,  A.  E.,  Comptes  rendus,  vol.  116, 1893,  p.  677. 
b ObalsM,  J.,  Jour. Canadian  Min.  lust.,  vol.  7. 1904,  p. 243;  Eng.and  Min.Jour.,  vol.  77, 1904, p.  141. 
Bewett,  Foster,  Hug. and  Min.Jour..  vol.  82, 1906,  p.  385.     Bravo,  Jose  J.,  Inform. y  Mem    Bol.  Sol 
Ing.  [Lima],  vol.  s.  1906,  p.  171. 
