50U  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull.  225. 
formed  at  the  Rabbit  Hole  sulphur  mines  it  has  been  removed  by  ero- 
sion. Evidence  of  the  action  of  thermal  springs  may  now  be  seen  in 
the  altered  rocks  through  which  the  waters  ascended. 
Mr.  Russell,  in  discussing  the  Rabbit  Hole  deposits,  expressed  the 
opinion  that  the  mines  lie  along  a  fault,  but  no  direct  evidence  of  a 
fault  at  the  locality  can  be  found.  Faulting,  however,  is  common  in 
the  region,  and  the  fracturing  accompanying  displacement  would  allow 
deep-seated  waters  and  sulphurous  gases  to  ascend.  In  this  region, 
where  volcanic  activity  has  been  so  important,  we  may  reasonably 
presume  that  it  is  the  cause  of  the  sulphur  deposits.  The  escape  of 
sulphurous  gases  may  have  been  contemporaneous  with  the  action  of 
the  springs  or  ma}7  have  occurred  subsequent  to  their  activity. 
Associated  minerals. — In  the  cavities  of  the  rock  formations  carrying 
sulphur  deposits  there  is  found  a  considerable  amount  of  white  pul- 
verulent material,  which  on  chemical  examination  proves  to  be  al unite. 
This  is  a  t^drous  sulphate  of  aluminum  and  potash,  a  mineral  which 
is  thought  to  be  formed  in  many  cases  by  the  reaction  of  sulphurous 
vapors  on  rocks,  especially  on  feldspars  that  carry  aluminum  and 
potash.  It  usually  occurs  at  places  where  solfataric  action  is  known 
to  have  taken  place,  and  the  fact  that  alunite  is  found  at  the  Rabbit 
Hole  sulphur  mines  may  be  regarded  as  supplementary  proof  of  the 
mode  of  origin  of  the  sulphur.  Alunite,  when  it  occurs  in  sufficient 
quantities,  may  be  used  as  the  source  of  alum,  its  chemical  composi- 
tion being  similar  to  kalinite,  or  native  alum. 
The  occurrence  of  a  small  amount  of  cinnabar  on  the  surfaces  of  the 
rocks  and  the  sulphur  has  already  been  noted.  This  mineral,  which  is 
mercuric  sulphide,  is  commonty  formed  by  solfataric  action,  and  its 
presence  is  an  additional  evidence  of  the  mode  of  origin  ascribed  to  the 
sulphur  deposits. 
Some  crystals  of  gypsum  were  seen  in  the  mines.  This  mineral, 
which  is  sulphate  of  lime,  may  be  formed  by  the  reaction  of  sulphuric 
acid  on  the  calcareous  material  of  the  rocks,  and  it  is  probably  of  late 
origin.  . 
Production. — The  output  of  the  Rabbit  Hole  sulphur  mines  is 
included  in  the  statistics  published  in  Mineral  Resources  of  the  United 
States  for  1902  by  the  U.  S.  Geological  Survey,  in  which  the  total 
production  of  the  country  is  stated  to  be  8,336  short  tons,  valued  at 
$220,560.  This  was  all  derived  from  Louisiana,  Nevada,  and  Utah, 
named  in  the  order  of  their  importance.  The  output  for  that  year  is 
the  largest  yet  recorded.  The  amount  of  sulphur  imported  during 
the  year  was  174,939  long  tons,  which  shows  that  the  percentage 
produced  in  the  United  States  is  but  a  small  amount  of  the  innual 
consumption.  In  spite  of  the  disadvantage  of  location  with  respect 
to  the  market  and  the  absence  of  duty  on  imported  sulphur,  the 
domestic  industry  promises  to  increase. 
