FELDSPAR    AND    QUARTZ    DEPOSITS    OF    MAINE.  391 
his  quarry  is  black  mica  (biotite)  in  lath-shaped  crystals  up  to  3  or  4 
eet  in  length.  Most  of  it  can  be  separated  readily  from  the  feldspar. 
Taraets  are  not  abundant.  Muscovite  or  white  mica  is  uniformly 
■f  the  A  variety  and  nowhere  of  commercial  grade.  It  is  concen- 
rated  principally  along  certain  planes  and  is  not  difficult  to  separate 
mm  the  highly  feldspathic  rock.  The  surrounding  rocks  at  this 
[uarry  are  metamorphic  schists,  probably  of  sedimentary  origin, 
rhich  dip  at  steep  angles  and  strike  slightly  east  of  north.  Next  to 
he  pegmatite  mass  the}^  have  been  much  injected  and  also  show 
igns  of  softening.  The  form  and  extent  of  the  pegmatite  body  can 
Lot  be  accurately  determined  because  of  a  scarcity  of  outcrops. 
The  smaller  quarry  one-half  mile  southwest  of  the  large  one  was 
pened  in  1906  and  covers  only  about  an  acre,  with  an  average  depth 
i  about  10  feet.  In  general  the  materials  are  similar  to  those  of  the 
irge  quarry.  Some  masses  of  pure  feldspar  are  10  feet  across. 
)utcrops  are  very  few  in  the  immediate  vicinity  of  this  quarry  and 
he  form  of  the  pegmatite  body  can  not  be  determined.  In  both  of 
hese  quarries  the  feldspar  is  mainly  cream  colored  and  of  the  potash 
arieties  microcline  and  orthoclase.  Crystals  of  white  feldspar  show- 
rig  twinning  striations  on  certain  of  their  faces  art  albite,  a  soda 
eldspar,  but  they  are  not  abundant. 
Another  quarry  within  a  few  rods  of  the  small  quarry  just  described 
s  worked  by  the  Maine  Feldspar  Company,  of  Auburn,  Me.  The 
•utput  is  very  small  and  the  character  of  the  rock  is  entirely  similar 
o  that  at  the  adjacent  quarries.  Feldspar  has  been  quarried  in  the 
>ast  at  several  other  points  in  this  vicinity,  notably  at  Mount  Ararat, 
Lear  Topsham  village. 
AUBURN  AND  POLAND,  ANDROSCOGGIN  COUNTY. 
The  third  important  feldspar  locality  is  Mount  Apatite,  in  the  town 
>f  Auburn,  about  6  miles  west  of  the  city  of  Auburn.  The  quarry 
Lere  is  worked  by  the  Maine  Feldspar  Company,  the  crude  spar  being 
lauled  by  team  about  2  miles  to  the  mill  at  Littlefield  station,  on  the 
jrand  Trunk  Railway.  This  mill  is  equipped  with  one  chaser  larger 
nan  that  used  in  most  spar  mills,  each  burrs  tone  weighing  3^  tons. 
Lne  ball  mill  also  is  longer  than  those  commonly  used  and  grinds  3 
ons  every  four  and  one-half  hours,  the  capacity  of  the  mill  being 
tbout  15  tons  in  twenty-four  hours. 
The  rock  mined  at  Mount  Apatite  is  taken  from  a  number  of  pits 
'5  to  150  feet  long,  about  50  feet  wide,  and  10  to  20  feet  deep.  These 
orm  part  of  a  single  mass  of  pegmatite  covering  most  of  the  summit 
>f  the  hill  and  intrusive  into  schists  of  probable  sedimentary  origin. 
Exposures  are  not  continuous  enough  to  trace  the  exact  outlines  of 
-he  mass,  but  its  greatest  extension  seems  to  be  in  a  north-northeast 
md  south-southwest  direction,  parallel  to  the  trend  of  the  surrounding 
