:oki:l.1  LTMONTTK    OF    ISTEW    YORK    AND    NEW    ENGLAND.  341 
cellist  dipping  steeply  (about  00°)  eastward,  while  limestone  occurs 
i  short  distance  east  of  the  mine  and  probably  forms  the  hanging 
vail  of  the  deposit.  The  clays  associated  with  the  ore  show  a  band- 
ng  parallel  to  that  of  the  adjoining  mica  schist.  Analyses  of  the 
>res  follow : 
Analyses  of  iron  ore  from  National  mine,  near  Pawling.  N.  Y. 
Metallic  iron 
^hosphorus 
Phosphorus  in  100  parts  iron 
43.22 
.113 
.261 
47.12 
.137 
.291 
ORIGIN    OF   THE    ORES. 
As  noted  in  the  mine  descriptions  given  above,  iron  carbonate  is  a 
'airly  constant  associate  of  the  brown  hematite.  In  several  of  the 
nines  this  carbonate  has  been  found  in  place  in  the  lower  workings. 
\t  the  Burden  mines,  near  Hudson,  N.  Y.,  a  body  of  practically 
maltered  iron  carbonate  appears  at  the  surface,  having  been  pro- 
ected  from  oxidation  by  a  heavy  covering  of  Hudson  shale.  It 
ccnis  probable,  therefore,  that  such  of  the  limonite  deposits  as  show 
ron  carbonate  in  depth  may  be  fairly  considered  to  owe  their 
►rigin  to  the  oxidation  of  this  carbonate.     In  the  Burden  mines,  as 
ell  as  at  other  points,  the  weight  of  evidence  seems  to  favor  the 
dea  that  the  iron  carbonate  is  not  an  original  deposit,  but  that  it  has 
'ormed  by  the  replacement  of  limestone.  This  point  will  be  dis- 
missed in  detail  in  another  place. 
Four  fairly  distinct  types  of  deposits,  so  far  as  mode  of  occur- 
ence are  concerned,  can  therefore  be  made  out.  The  method  of 
>rigin  of  the  first  three  named  can,  it  is  believed,  be  stated  with  some 
ertainty.     The  fourth  type,  however,  is  by  no  means  so  readily  deter- 
Inined,  and  it  is  probable  that  it  has  originated  at  different  locali- 
ies  in  very  different  ways.  This  supposition  is  confirmed  by  the 
esnlts  obtained  by  Hayes  in  Alabama  and  Georgia.  It  may  be 
urther  pointed  out  that  while  types  1,  2,  and  3  are,  on  the  whole, 
lost  likely  to  occur  in  a  sharply  folded  district  with  steeply  dip- 
)ing  strata,  type  4  is  much  more  likely  to  be  found  in  a  gently 
olded  area.  This  may  account  for  its  lack  of  importance  in  the 
rea  discussed  in  this  paper  and  for  its  great  abundance  both  in 
sTe\v  York  and  Pennsylvania,  as  well  as  farther  south.  The  proba- 
le  methods  of  origin  of  the  four  types  noted  are  as  follows: 
7'///;/  /. — Originating  in  the  replacemenl  by  iron  carbonate  of  a 
bin  bed  of  limestone  occurring  /'//  the  Hudson  series  of  shales  and 
chists.     Ore  I J ill  mines. 
