176 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1903.  [bvll.  225. 
to  some  extent.  On  the  southwest  slope  of  the  same  mountain  toward 
Potter  Creek  numerous  prospects  showed  a  large  amount  of  copper 
staining,  but  when  examined  no  definite  bodies  of  copper  ore  had 
been  disclosed.  The  Mineral  Wealth  of  northern  California  recently 
reports  that  the  Bully  Hill  Company  has  bonded  some  of  these  claims. 
AFTERTHOUGHT    DISTRICT. 
Copper  Hill  lode.  This  locality  was  worked  years  ago  and  lately 
revived,  but  is  not  yet  producing.  It  consists,  so  far  as  known,  of 
two  short,  nearly  vertical  ore  bodies — the  Copper  Hill  and  the  After- 
thought lodes — which  strike  about  K  55°  W.  parallel  to  the  Copper 
City  arch.  The  two  bodies  are  nearly  parallel  and  are  approximately 
350  feet  apart  en  echelon,  and  one  of  them  has  been  prospected  to  a 
depth  of  over  100  feet.  They  lie  close  to  the  contact  in  metarhyolite 
that  incloses  fragments  of  slate,  and  the  ores,  like  some  of  those  found 
elsewhere,  are  composed  largely  of  pyrite,  sphalerite  with  chalcopyrite 
and  galena,  and  local  traces  of  bornite.  The  gangue,  less  than  5  per 
cent  of  the  ore,  is  barite  with  a  trace  of  calcite. 
In  the  Black  Diamond  district  and  the  Roseman  group  of  prospects 
there  has  been  scarcely  any  development  work  during  the  year,  but 
farther  south  along  the  western  edge  of  the  McCloud  limestone  the 
Memorial  prospects  have  been  extended  with  no  important  discoveries 
at  the  time  of  examination. 
LIMESTONE. 
The  limestone  of  the  Redding  quadrangle  was  briefly  noted  last  year 
in  Bulletin  213,  page  315.  The  McCloud  limestone,  near  the  United 
States  fishery  at  Baird,  was  formerly  used  for  flux  at  Bully  Hill,  but 
in  1903  the  material  for  that  purpose  was  obtained  from  the  Hosselkus 
limestone  of  Brocks  Mountain,  about  6  miles  northeast  of  Delamar. 
Mr.  J.  B.  Keating,  the  general  superintendent  at  Bully  Hill,  has  kindly 
furnished  the  following  partial  analyses  of  these  limestones: 
Partial  analyses  of  McCloud  and  Hosselkus  limestones. 
McCloud. 
Hosselkus. 
CaO 
Per  cent. 
52.5 
}      L" 
2.0 
Per  cent. 
51.0 
Fe203 
A1203 
1.5 
Insoluble 
4.0 
The  McCloud  limestone  contains  nearly  94  per  cent  of  carbonate  of 
lime,  while  the  Hosselkus  contains  less  than  92  per  cent,  but  both  are 
said  to  be  good  for  the  purpose  for  which  they  are  used. 
