keith.]  KECENT    ZINC    MINING    IN    EAST    TENNESSEE.  209 
smaller  streams  is  derived  from  springs,  whose  flow  is  only  stopped 
by  severe  droughts.  In  the  areas  underlain  by  limestone  much  of 
the  drainage  is  underground,  and  the  water  reappears  from  place  to 
place  in  bold  springs. 
Rock  formations. — The  rocks  of  this  portion  of  the  valley  are  all  cal- 
careous, and  include  limestone,  dolomite,  and  shale.  The  zinc  deposits 
are  found  in  the  Knox  dolomite,  the  principal  formation  of  the  region, 
which  consists  of  massive  limestones  and  dolomites,  more  or  less  cherty. 
These  have  various  colors,  ranging  from  blue,  gray,  and  dove  colored 
to  nearly  white.  Above  this  formation  are  the  blue  and  gray  Chicka- 
mauga  limestones.  These  in  turn  are  succeeded  by  the  Holston 
marble,  consisting  of  variegated  marbles  of  a  general  red  or  gray 
color.  The  zinc  deposits  are  found  in  the  upper  part  of  the  Knox 
dolomite  and  not  far  below  the  Chickamauga  limestone.  The  lower 
portion  of  the  Knox  dolomite  is  of  Cambrian  age,  but  all  the  strata 
near  the  zinc  deposits  are  Ordovician. 
Structure. — The  rocks  of  the  East  Tennessee  Valley  are  seldom 
found  in  a  horizontal  position,  but  are  bent  into  folds  of  various  angles 
and  broken  by  faults.  These  structures  have  a  general  northeast-south- 
west trend,  and  cause  the  belts  of  rock  to  outcrop  in  similar  courses. 
One  of  the  principal  synclinal  folds  of  the  region  passes  a  few  miles 
south  of  the  zinc  deposits,  so  that  the  rocks  inclosing  the  zinc  ores 
have  a  general  dip  to  the  south  toward  its  axis.  The  amount  of  dip 
varies  considerably — from  40°  to  45°  near  Knoxville  to  10°  or  20°, 
or  even  less,  in  the  vicinity  of  Newmarket  and  Jefferson  City.  Minor 
rolls,  or  flat  arches,  form  exceptions  to  the  general  southerly  dip,  but 
do  not  appear  to  have  any  close  relation  to  the  zinc  deposits.  At  New- 
market and  Jefferson  City  the  zinc-bearing  rocks  are  near  the  plane  of 
a  great  overthrust  fault.  That  they  are  possibly  all  of  the  same  origin 
would  seem  to  be  borne  out  by  the  nature  of  the  deposits  themselves, 
which  are  in  all  cases  formed  in  broken  or  brecciated  strata.  In  gen- 
eral, however,  only  the  most  limited  brecciation  is  to  be  observed 
along  the  faults  of  this  region.  Toward  the  southwest  end  of  the 
belt,  moreover,  there  is  no  such  association  of  the  faults  with  the 
deposits,  so  that  a  common  origin  is  not  likely. 
Developments. — As  already  stated,  the  existence  of  the  zinc  ore  in 
this  region  has  been  known  for  many  years.  The  ores  have  the  same 
features  in  all  cases;  carbonate  and  silicate  of  zinc  near  the  surface  are 
succeeded  by  the  sulphide  10  or  20  feet  downward.  About  twenty 
years  ago  many  openings  were  made  and  considerable  rock  was  blasted 
out  on  Spout  Run,  about  2  miles  west  of  Mascot  station,  on  the  Southern 
Railway,  and  also  \\  miles  west  of  Mascot,  where  the  Roseberry  Zinc 
Company  is  now  operating.  Work  in  these  places  was  practically 
limited  to  the  more  easily  treated  carbonate  ores.  A  great  many  test 
pits  were  sunk  within  a  few  miles  to  develop  the  extent  of  the  ore. 
Bull.  225—04 14 
