BUILDING  STONE  AND  ROAD  METAL. 
NOTE  ON  A  NEW  VARIETY  OF  MAINE  SLATE. 
Bv  T.  Nelson  Dai 
In  September,  1905,  the  writer  made  a  trip  with  Dr.  George  Otis  Smith,  of  the  United 
States  Geologieal  Survey,  and  Prof.  Leslie  A.  Lee,  State  geologist  of  Maine,  to  a  slate  pros- 
pect said  to  have  been  opened  in  1890  in  the  town  of  Forks,  Somerset  County,  in  central 
Maine,  between  Kennebec  and  Piscataquis  rivers. 
This  prospect  lies  in  the  broad  belt  of  Paleozoic  slate  which  Prof.  C.  II.  Hitchcock's 
geological  map  of  1885  shows  as  extending  from  the  Kennebec  to  Schoodic  Lake  and 
beyond,  and  which  includes  the  slate  quarries  of  Brownville,  Monson,  and  North  Blanchard. 
The  location  of  this  slate  deposit  is  about  longitude  69°  57',  latitude  45°  16',  or  about  18 
miles  west  of  the  North  Blanchard  quarries,  in  the  southwest  corner  of  the  town  of  Forks, 
about  3  miles  northeast  of  Caratunk,  over  a  mile  about  northwest  of  the  hotel  on  Pleasant 
Pond,  about  half  a  mile  from  the  Washington  Schoolhouse,  1,090  feet  above  sea  level,  on 
Holly  Brook,  on  land  owned  by  Lawrence  Hill.  The  nearest  railroad  is  the  Somerset 
Railway  Extension  at  Mosquito  Narrows,  6  miles  distant. 
The  slate  crops  out  in  the  bed  of  the  brook,  being  exposed  for  a  thickness  of  30  feet  or 
more  across  the  cleavage.  The  excavation  appears  to  have  been  from  10  to  15  feet  deep. 
The  cleavage  strikes  N.  55°  E.  and  dips  from  steep  northwest  to  90°,  but  in  the  upper  10 
feet  there  is  a  fold  resulting  in  a  steep  southeast  dip.  The  course  of  the  bedding  could  not 
be  determined,  hut  (he  microscopic  examination  affords  indications  that  it  is  nearly  parallel 
to  the  cleavage. 
The  slate  is  bluish  black,  of  fine  texture  and  cleavage  surface,  with  a  luster  not  so  great 
as  l  hat  of  the  Brownville  slate,  but  yet  bright.  It  is  graphitic,  contains  a  very  small 
amount  of  magnetite,  lias  no  argillaceous  odor,  does  not  effervesce  in  cold  dilute  hydro- 
chloric acid,  is  quite  sonorous,  and  is  readily  perforated.  Neither  the  ledge  nor  the  frag- 
ments exposed  for  fifteen  years  show  discoloration. 
Under  the  microscope  the  section  shows  a  matrix  of  muscovite  (sericite)  with  a  brilliant 
aggregate  polarization,  proving  it  to  be  a  mica-slate.  The  cleavage  is  fine  and  regular. 
The  next  conspicuous  feature  is  the  presence  of  about  52  lenses  of  pyrite  to  each  square 
millimeter,  measuring  (in  transverse  section)  from  0.02  to  0.0G  mm.  in  length  by  0.004  to 
0.016  mm.  in  width.  In  sections  parallel  to  the  cleavage  these  lenses  have  a  very  irregular 
outline  and  are  often  as  broad  as  long.  They  account  for  the  limonitic  staining  on  cleavage 
surfaces  of  water-soaked  specimens.  Quartz  is  abundant  but  minute.  No  carbonate 
could  be  detected.  A  few  tourmaline  prisms  up  to  0.11  mm.  in  length  occur.  Some  scales 
of  chlorite  with  interleaved  muscovite  measure  up  to  0.09  mm.  Occasional  zircon  frag- 
ments and  aggregations  of  rutile  crystals  appear. 
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