weed.]  HOT    SPRINGS   AND    HOT-SPRING   DEPOSITS.  601 
but  the  main  outflow  is  from  the  open  quarries  and  underground 
workings,  where  a  deposit  of  limonite  is  extracted  for  a  flux. 
This  limonite  deposit  is  extensive,  covering  many  acres.  It  comes 
to  the  surface  in  some  places,  but  elsewhere  lies  beneath  the  traver- 
tine sheet,  of  which  it  is  clearly  a  replacement  formed  by  the  exist- 
ing springs. 
The  travertine  has  the  surficial  aspect  of  an  ordinary  limestone. 
Even  in  the  cuts  along  the  switch  line  to  the  new  smelter,  where  20 
feet  of  curved  and  platy  superimposed  sheets  of  calcareous  tufa  are 
exposed,  the  travertine  is  easily  mistaken  for  limestone  unless  com- 
pared with  the  similar  old  deposits  of  the  Yellowstone  Park.  Aside 
from  the  water-filled  cone  just  noted,  there  are  no  recent  deposits  to 
give  a  clue  to  its  origin.  The  old  basins  and  terraces  are  gone,  soil 
and  vegetation  cover  a  large  part  of  the  area,  and  the  travertine  is  no 
longer  loose  and  friable,  but  hard  and  dense,  though  in  part  still 
porous. 
The  chief  economic  interest  lies  in  the  iron  ore.  The  existing 
waters  are  distinctly  ferruginous  and  are  warm  (100°d=  ).  They  de- 
posit limonite  in  their  channels  and  in  the  drainage  trenches,  and 
are  evidently  replacing  the  travertine  by  limonite  (not  siderite)  at 
a  depth  of  10  to  20  feet  below  the  surface.  The  limonite  not 
only  forms  a  sheet,  but  sac-shaped  masses,  prongs,  and  tongues  pro- 
ject into  the  travertine  along  joint  cracks,  etc.  This  ore  is  very  low 
in  silica,  carries  2  per  cent  or  more  of  lime  (gradations  to  travertine 
being,  of  course,  common ) ,  and,  according  to  assays,  often  carries  50 
cents  to  $1.50  in  gold  per  ton.  It  is  the  chief  source  of  flux  for  the 
great  Washoe  copper  smelter. 
GYPSUM  VEINS  AND  WATERS  OF  HUNTERS  HOT  SPRINGS,  MONT. 
The  gypsum  veins  at  Hunters  Hot  Springs,  Mont,,  are,  so  far  as 
known,  devoid  of  metallic  contents,  but  are  of  considerable  scientific, 
and  possibly  economic,  importance.  Gypsum  is  often  found  in  min- 
eral veins,  but  has  usually  been  considered  as  an  alteration  product, 
due  to  oxidizing  waters,  which  become  acid  from  decomposing  sul- 
phides, and  read  on  carbonate  of  lime.  That  the  gypsum  at  Hunters 
Hot  Springs  is  of  primary  origin  and  is  due  to  deposition  by  hot 
waters  in  open  fissures  appears  certain. 
One  of  the  best-known  hot-spring  resorts  of  Montana  is  situated  on 
the  hills  north  of  the  YelloAvstone  River,  about  20  miles  east  of  Liv- 
ingston. The  locality  is  easily  accessible  from  a  station  on  the  North- 
ern Pacific  Railroad,  and  is  improved  by  hotels  and  bath  houses. 
The  area  is  part  of  the  foot-slope  region  of  the  Crazy  Mountains, 
