STONE. 
During  the  last  year  many  important  quarry  districts  were  exam- 
ined by  members  of  the  Survey.  Particular  attention  was  given  to 
the  slate  industry,  and  a  Survey  bulletin  on  the  slate  deposits  and  slate 
industry  of  the  United  States  is  now  in  course  of  preparation.  Brief 
papers  on  several  important  western  slate  districts  are  presented 
below.  During  1904  it  is  planned  to  have  examinations  made  of  the 
slate  deposits  of  Maine,  Arkansas,  Virginia,  and-  Minnesota,  and  to 
review  the  slate  deposits  of  other  sections  of  the  country  which  have 
previously  been  reported  on.  It  will  then  be  possible  to  issue  a  com- 
prehensive report  on  the  slate  industry. 
NOTE  ON  ARKANSAS  ROOFING  SLATES, 
By  T.  Nelson  Dale. 
A  few  specimens'  of  black,  reddish,  and  greenish  roofing  slate  from 
Polk  County,  Ark.,  received  at  the  office  of  the  United  States  Geo- 
logical Survey,  were  referred  to  the  writer  for  microscopic  examina- 
tion. Polk  County  borders  on  the  Indian  Territory  and  lies  about 
midwa}^  between  Red  and  Arkansas  rivers.  The  results  of  this  exami- 
nation are  as  follows: 
1.  Black  -slate  (phyllite)  from  Mena,  near  Big  Forks. — This  is  a 
black  sonorous  slate  with  a  remarkably  smooth  cleavage  surface  and 
a  very  line  cleavage.  The  aggregate  polarization  is  very  brilliant, 
indicating  complete  sericitization  of  the  matrix.  The  texture  is 
unusually  tine  and  the  matrix  very  homogeneous.  Quartz  grains  do 
not  exceed  0.01  millimeter  in  diameter.  The  "slate  needles"  (Ti02) 
are  unusually  minute.  Carbonaceous  matter  in  particles  of  various 
sizes  accounts  for  the  color.  There  is  no  carbonate  present,  nor  is 
there  any  effervescence  in  cold  dilute  hydrochloric  acid.  A  little 
pyrite  is  present.  There  is  no  trace  of  false  cleavage.  This  is  a  very 
superior  quality  of  roofing  slate,  splitting  readily,  and  not  liable  to 
discoloration  on  exposure. 
414 
