FELDSPAR    AND    QUARTZ    DEPOSITS    OF    MAINE.  387 
has  recently  been  aroused  in  the  use  of  potash  feldspar  for  fertilizing 
purposes.  Potash  is  an  important  plant  food  which  in  fertilizers 
has  usually  been  applied  in  the  form  of  easily  soluble  potash  salts 
imported  from  Germany.  Recent  experiments  conducted  by  the 
Department  of  Agriculture  have  shown  that  certain  plants  are  capa- 
ble of  readily  decomposing  feldspar  that  has  been  ground  to  the  fine- 
ness usually  demanded  in  the  pottery  industry  (200  mesh  and  finer). 
The  Department  of  Agriculture  is  now  carrying  on  an  exhaustive 
series  of  experiments  to  determine  what  plants  are  benefited  by  the 
use  of  feldspar  and  the  exact  character  of  the  materials  needed,  and 
to  avoid  failures  due  to  the  misuse  of  these  materials  it  is  safer  for 
fertilizer  manufacturers  and  others  to  await  the  published  report  on 
these  tests. 
QUARTZ. 
At  present  (1906)  there  is  no  market  for  the  quartz  mined  in  Maine, 
even  when  produced  as  an  accessory  in  feldspar  mining.  At  some 
of  the  mines  it  is  thrown  on  the  waste  heaps ;  at  others  it  is  collected 
in  piles  in  the  hope  of  a  future  market.  It  formerly  found  a  some- 
what unsteady  market  for  pottery  and  sandpapei  purposes.  The 
low  value  of  the  crude  material,  about  $2  per  ton  at  the  mines,  makes 
it  impossible  for  Maine  quartz  to  compete  with  quartz  from  Connecti- 
cut, New  York,  Pennsylvania,  and  Maryland  quarries,  which  are 
nearer  to  the  markets. 
METHODS  OF  MANUFACTURE. 
Feldspar  is  ground  at  two  mills  in  Maine — one  at  Cathance  station, 
near  Brunswick,  operated  by  the  Trenton  Flint  and  Spar  Company, 
of  Trenton,  N.  J.;  the  other  at  Littlefield  station,  near  Auburn,  oper- 
ated by  the  Maine  Feldspar  Company.  The  method  of  grinding  is 
similar  at  both  of  these  mills  and  is  the  same  as  that  generally  used 
by  feldspar  and  quartz  grinders  elsewhere  in  the  United  States.  The 
lump  material  as  it  comes  from  the  quarries  is  first  crushed  in  a 
chaser  mill,  of  which  each  factory  usually  has  several.  This  consists 
of  two  burrstone  wheels  about  3  to  5  feet  in  diameter  and  1  to  H 
feet  thick  attached  to  each  other  like  the  wheels  of  a  wagon  by  a 
horizontal  axle.  This  axle  is  attached  at  its  center  to  a  rotating  verti- 
cal shaft  which  causes  the  wheels  to  travel  over  a  burrstone  bed,  the 
feldspar  being  crushed  between  the  two  burrstone  surfaces.  The 
material  as  it  comes  from  this  mill  is  screened,  the  tailings  being 
returned  to  the  chaser  mills  for  recrushing  and  the  fines  going  to  ball 
mills  for  their  final  grinding.  The  ball  mills  consist  of  steel  cylin- 
ders revolving  on  a  horizontal  axis.  They  are  usually  lined  either 
with  wooden  blocks  or  blocks  made  of  highly  siliceous  brick  and 
are  charged  with  pebbles  of  Norway  or  French  flint  2  to  3  inches  in 
