424  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.8S. 
The  unstratified  or  igneous  rocks  underlie  the  stratified  rocks,  or  are 
pushed  up  through  them,  and  include  granitic  and  basaltic  rocks, being 
generally  found  in  the  form  of  dikes.  Discordances  between  slaty 
cleavage  and  bedding  are  found.  The  crystalline  structure  of  the  Pri- 
mary stratified  rocks  is  supposed  to  be  due  to  heat  which  comes  from 
the  contact  of  the  underlying  intensely  heated  granite.  These  forma- 
tions have  no  invariable  order  of  superposition,  although  they  generally 
overlie  each  other  in  the  following  manner :  Clay  slate,  talcose  slate, 
mica-slate,  hornblende-slate,  gneiss;  and  associated  with  these  are 
also  beds  of  limestone,  quartz,  chlorite,  slate,  and  soapstone. 
A  very  massive  gneiss,  known  as  "  table  rock,"  on  the  west  side  of 
Saluda,  rests  unconforinably  upon  the  slates,  and  is  regarded  as  evi- 
dence of  the  prior  deposition  of  the  slates,  and  also  as  evidence  of  a 
time  break  between  the  two.  The  mica- slates  pass  by  insensible  gra- 
dations into  the  talcose  slates.  The  lime  rock  is  interlaminated  both 
with  gneiss  and  with  mica-slates,  the  latter  occurring  at  Kings  moun- 
tain. The  quartz  rocks  are  regarded  as  residual  material  left  by  the 
disappearance  of  the  micaceous  and  talcose  portion  of  the  rock.  It 
sometimes  passes  into  a  conglomerate-like  phase,  but  this  is  a  step 
on  the  way  toward  complete  crystallization.  The  quartz  rock  at  times 
passes  into  itacoluniite.  The  magnetic  and  hematitic  ores  are  asso- 
ciated mostly  with  the  slates  and  limestones,  and  appear  as  beds 
interlaminated  with  and  grading  into  them. 
Lieber,  202  in  1858,  describes  the  rocks  of  Chester  and  York  districts. 
They  are  divided  into  clay-slate,  which  includes  limestone,  itacoluniite, 
and  specular  schist;  and  hornblende-slate,  which  includes  talcose  slate 
and  mica-slate.  The  first  class,  which  may  possibly  be  Paleozoic,  ap- 
pears wherever  the  Tertiary  deposits  have  been  removed  by  erosion. 
It  has  a  dip  unconformable  to  the  talcose  slate.  Itacoluniite  is  de- 
scribed, and  below  it  at  times  are  found  specular  schist  and  above  it 
limestone.  The  igneous  rocks  are  divided  into  trachytic,  trappean, 
and  granitic  rocks.  The  trachytic  rocks  include  eurite,  quartz-por- 
phyry, coarse  trachyte,  domite,  and  phonolith;  the  trappean  rocks  in- 
clude diorite,  diorite- slate,  soapstone  (?),  talcose  trap  (?),  melaphyre, 
and  aphanitic  porphyry;  the  granites  include  coarse  grained  granite, 
syenite,  and  other  granite  and  gneiss. 
Lieber,203  in  1858,  divides  the  rocks  of  Union  and  Spartanburg  into 
a  Super-itacolumite,  ltacolumite,  and  Sub-itacolumite  groups.  The  first 
includes  limestone.  The  second  includes  itacolumite  with  talcose  slate, 
limestone,  specular  schists,  and  itacolumite  conglomerate.  The  third 
includes  clay -si  ate,  talcose- si  ate,  mica-slate,  and  gneiss.  There  is  no 
definite  proof  that  the  gneiss  occupying  the  lowest  position  is  of  sedi- 
mentary origin.  Indeed  there  is  greater  probability  that  it  is,  strictly 
speaking,  a  granite  having  a  parallel  distribution  of  the  scales  of  mica. 
It  passes  into  the  ordinary  granite,  with  no  distinct  boundary  between 
the  two.    The  mica-slate  overlying  the  gneiss  is  of  insignificant  thick- 
