PIEDMONT  PLATEAU  AND  PORTIONS  OP  THE  APPALACHIANS.       703 
is  very  schistose  and  the  phenocrysts  are  much  broken  and  elongated. 
The  foliation  planes  have  a  very  constant  dip  in  this  formation. 
Beech,  granite. — This  granite  cuts  the  Cranberry  granite  and  the 
Blowing  Rock  gneiss.  The  formation  consists  of  coarse,  red  or  gray 
massive  granite  marked  by  biotite  and  of  a  very  coarse,  Light  variety 
with  orthoclase  phenocrysts.  Large  amounts  of  the  rock  are  only 
slightly  metamorphosed,  hut  most  of  the  formation  is  schistose.  The 
phenocrysts  are  elongated  and  the  massive  varieties  are  striated  and 
flattened  into  schists. 
Max  Patch  granite. — The  Max  Patch  cuts  the  Cranberry  granite, 
the  Roan  gneiss,  and  the  Carolina  gneiss.  This  granite  is  decidedly 
like  the  Beech  granite,  hut  the  two  are  not  in  contact.  The  varieties 
of  each  are  about  the  same  and  each  is  metamorphosed  to  the  same 
extent.     It  is  possible  that  they  are  derived  from  the  same  magma. 
Linville  metadiabase. — This  formation  occurs  in  dikes  cutting  the 
Cranberry  granite  and  the  Blowing  Rock  gneiss,  and  also  forms  large 
bodies  which  appeal'  to  grade  into  the  Montezuma  schist.  The  meta- 
diabase is  of  a  greenish  color  and  is  composed  mainly  of  plagioclase 
and  hornblende.  With  these  are  much  epidote,  chlorite,  and  fibrous 
hornblende.  In  some  places  the  original  structures  remain;  in  others 
the  secondary  schistosity  and  epidote  lenses  are  most  prominent. 
Montezuma  schist. — This  formation  is  chemically  similar  to  meta- 
diabase and  appears  to  be  the  upper  part  of  the  same  igneous  mass. 
It  consists  of  fine  schists  and  amygdaloids,  of  bluish  or  greenish  color, 
which  are  composed  mainly  of  chlorite,  feldspar,  epidote.  muscovite, 
and  quartz.  These  are  all  nietamorphic  minerals  and  the  rock  is 
decidedly  schistose.  The  lenses  of  epidote  and  quartz  are  very  promi- 
nent and  often  of  large  size.  The  amygdaloids  are  plainly  vesicular 
surface  lavas,  but  no  traces  of  a  glassy  base  remain. 
Gatoctin  schist.  This  schist  is  prominent  in  Maryland  and  north- 
ern Virginia  and  is  similar  in  every  respect  to  the  Montezuma  schist. 
Flattop  schist. — This  rock  cuts  the  Cranberry  granite  and  the 
Blowing  Rock  gneiss.  It  consists  of  dark  bluish  or  black,  banded 
schists  with  some  amygdaloid.  The  component  minerals  are  feld- 
spar, quartz,  muscovite,  and  chlorite,  with  magnetite  and  epidote  in 
certain  layers.  Quartz,  feldspar,  and  muscovite  form  thin  gray 
bands  in  the  schist  and  represent  layers  of  volcanic  ash.  Flow  band- 
ing and  feldspar  phenocrysts  are  common  in  this  rock.  No  glassy 
base  is  now  to  be  seen  and  most  of  the  minerals  are  nietamorphic. 
The  formation  shows  a  transition  into  the  Montezuma  schist. 
Andesite. — This  rock  appears  in  Maryland  and  northern  Virginia 
in  many  small  areas.  In  all  respects  it  resembles  the  Flattop  schists, 
and  each  is  probably  metamorphosed  from  andesite. 
Metarhyolite.  This  rock  cuts  the  Carolina  gneiss.  Cranfcrerry  gran- 
ite, Blowing  Rock  gneiss,  and  apparently  the  Linville  metadiabase 
