206  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
calcio-volborthite,  highly  arsenical,  and  another  is  a  new,  hydrous, 
copper  vanadate,  distinct  from  volborthite  and  calcio-volborthite. 
Occurrence  of  the  ores. — Both  the  vanadium  crystals  and  the  asso- 
ciated amorphous  carnotite  occur  along  the  previously  mentioned 
strong  northeast-southwest  fracture  zone,  coating  walls  of  cracks  and 
within  certain  beds  of  sandstone.  The  fracture  zone,  5  to  25  feet 
in  width,  is  the  main  line  of  deformation  in  the  region.  It  traverses 
the  country  in  a  N.  00°  E.  direction,  and  dips  to  the  southeast  at  an 
angle  of  70°. 
The  rocks  which  it  cuts  are  well-bedded,  brownish-red,  gray,  and 
white  sandstone,  with  a  little  olive  shale.  They  dip  generally  to  the 
northwest  at  angles  ranging  from  35°  to  40°.  In  the  immediate 
vicinity  of  the  fracture  they  are  shattered,  fissured,  and  faulted. 
Faulting  on  the  main  fissure  has  brought  green  shale  in  the  foot 
Avail  against  gray  sandstone  in  the  hanging  wall.  The  sandstone 
dips  normally  to  the  northwest,  but  the  beds  in  the  foot  wall 
have  been  intensely  crushed  and  sheared  and  now  stand  at  high  an- 
gles for  a  distance  of  at  least  20  feet  west  of  the  fault.  The  amount 
of  dislocation  is  not  apparent  on  this  property,  but  the  direction 
may  have  been  downward  on  the  west  or  foot-wall  side.  Stratigraph- 
ically  these  beds  probably  lie  at  about  the  base  of  the  main  red  sand- 
stone series  and  thus  a  short  distance  above  the  conglomeratic  scries. 
The  vanadium  crystals  are  characteristically  found  in  thin  patches, 
1  to  10  inches  in  diameter,  upon  the  walls  of  sandstone  blocks  in  the 
shattered  zone.  They  arc  most  abundant  next  to  the  main  fissure. 
YelloAV  crystalline  material,  ranging  in  color  from  orange  to  canary 
yellow,  also  occurs  in  this  manner,  and  some  amorphous  carnotite  is 
occasionally  found  there.  The  more  usual  mode  of  occurrence  of  the 
carnotite,  however,  is  in  small  oval  masses,  one-sixteenth  to  1  inch 
in  diameter,  along  certain  beds  of  gray  sandstone  in  the  hanging 
wall.  These  bodies  are  also  most  abundant  adjacent  to  the  fissure, 
but  are  found  as  far  away  as  development  has  proceeded,  about  4 
feet.  As  regards  their  origin,  it  is  sufficient  for  present  purposes  to 
state  that  the  mineral  now  appears  from  general  aspect  to  have  been 
formed  by  replacement  of  the  sandstone,  as  a  complete  and  gradual 
transition  series  may  be  traced  from  unaltered  gray  sandstone  to  pure 
amorphous  carnotite.  On  the  Avails  of  the  oval  cavities  in  which  this 
carnotite  is  found  small  clusters,  rosettes,  and  Avreaths  of  the  dark- 
green  variety  of  vanadium  crystals  frequently  occur.  This  is  the 
most  intimate  relationship  between  the  A7anadiferous  and  uraniferous 
minerals  observed,  and  appears  to  indicate  an  earlier  date  of  de- 
position for  the  vanadiiVrous  compounds.  On  some  of  the  specimens 
of  yelloAvish-green  crystals  minute  pieces  of  a  robin's-egg  blue  min- 
eral appear,  which  resemble  bits  of  silk  thread  in  luster,  structure, 
