Copper  also  occurs  in  veins  and  deposits  associated  with  the  various
copper  minerals,  azurite,  malachite,  cuprite,  chalcopyrite,  bornite,  chalcocite,
etc.  Some  of  the  other  localities  for  the  occurrence  of  native  copper  are  the
Ural  Mountains,  Siberia ;  Nassau,  Germany ;  Cornwall,  England  ;  Chile ;  Bo-
livia ;  Peru ;  Brazil,  and  Australia.  In  small  quantities  in  various  places  in
Massachusetts,  Connecticut,  New  Jersey,  California;  more  abundantly  in
Arizona  and  New  Mexico.
Metallic  copper,  as  is  well  known,  is  used  very  extensively  in  commerce.
It  is  worth,  April  1910,  about  13  cents  per  pound.  Large  amounts  are
used  in  the  manufacture  of  copper  wire,  nails  and  sheets,  various  alloys,
electrical  apparatus,  also  for  coinage  purposes  and  chemical  reagents.
SILVER,  Native  Silver,  Ag.
Cubic,  hexoctahedral  class.  Cube,  octahedron,  rhombic  dodecahedron
and  tetrahexahedron  (m  =  2)  are  most  commonly  observed  as  inde-
pendent or  predominating  forms.  Crystals  are  very  small  and  often  dis-
torted. Twins  according  to  the  Spinel  law.  Also  acicular,  reticulated  or
arborescent.  Often  fine  threads  or  wires,  sometimes  matted  resembling  tufts
or  wads  of  hair  or  moss.  Masses,  plates,  and  scales.
No  cleavage  but  malleable  and  ductile.  Hardness  2.5  to  3  and  specific
gravity  10  to  12;  pure  10.52.  Metallic  luster.  Color  silver  white,  usually
with  yellow  brown,  gray  or  black  tarnish  colors.  Thin  sheets  appear  blue
in  transmitted  light.  Streak  metallic  silvery  white.  Excellent  conductor
of  heat  and  electricity.
Silver,  usually  with  varying  amounts  of  gold,  as  high  as  28%,  further-
more copper,  arsenic,  antimony,  mercury,  iron,  platinum,  etc.  Easily  fusible,
also  soluble  in  nitric  acid.
Occurs  commonly  with  ores  of  silver,  lead,  arsenic,  cobalt,  and  nickel.
