422  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1903.  [bull. 225. 
good  quality,  have  been  described  as  occurring  on  the  islands  in  Great 
Salt  Lake  and  some  attempt  has  been  made  to  develop  these  deposits. 
The  locality  which  has  been  most  widely  discussed,  however,  is  that 
mar  Provo.  This  has  been  exploited  to  some  extent  by  F.  W.  C. 
I  [athenbuck,  of  Provo.  The  slate  deposits  occur  about  2  miles  south- 
cast  of  Provo  station,  in  Slate  Canyon.  The  slate  here  covers  a  con- 
siderable area,  but  that  exposed  at  the  surface  is  so  badly  broken  up 
that  large  slabs  can  not  be  obtained.  It  is  possible,  however,  that  this 
condition  will  disappear  if  the  deposits  are  worked  deeper. 
The  Provo  deposits  furnish  green  and  purple  slates,  the  latter  being 
apparently  present  in  greater  quantity.  The  green  slates  show  little 
tendency  to  cleavage  in  their  surface  outcrops,  and  will  probably  be 
less  satisfactory  for  roofing  purposes  than  the  purple.  The  green 
slates  rub  very  smoothly,  however,  and  would  make  good  slabs  or  mill 
stock  if  obtainable  in  masses  of  sufficient  size. 
The  purple  slates  split  well,  with  a  surface  about  as  smooth  as  that  of 
Peach  Bottom  (Penna.-Md.)  slate.  From  samples  seen  it  appears  that 
they  also  bear  punching  well. 
A  specimen  of  the  purple  slate  selected  by  the  writer  was  anatyzed 
by  Mr.  W.  T.  Schaller  in  the  laboratory  of  the  United  States  Geological 
Survey,  the  results  being  as  follows: 
Analysis  of  purple  slate,  Provo,  Utah. 
Per  cent. 
Silica  ( Si02 ) 54.  05 
Alumina  (A1203) 20.  95 
Iron  oxides  (FeO,  Fe203) 28 
Lime  (CaO) 22 
Magnesia  (MgO^ 9. 12 
Carbon  dioxide  (C02)|                                                                                o  qq 
Water f  * " " 
Of  a  series  of  36  analyses  of  American  roofing  slates  collected  and 
discussed  a  recently  by  the  writer,  the  above  slate  from  Provo  stands 
lowest  in  its  percentages  of  silica  and  magnesia,  while  its  lime  is  very 
far  below  the  average. 
Nothing  definite  is  known  as  to  the  geologic  age  of  these  slates, 
though  they  are  supposed  to  be  Ordovician,  or  even  older. 
«Jour.  Geol.,  vol.  12,  1901,  p.  26. 
