MICA   IN    THE    HAKTVILLE    UPLIFT,  WYOMING.  425 
feet  to  the  west,  but  widens  to  50  feet  500  feet  still  farther  west. 
The  pegmatite  varies  considerably  in  the  size  of  its  constituent  min- 
erals. Muscovite  occurs  in  plates  up  to  20  inches  in  diameter, 
although  the  largest  plates  are  commonly  ruled.  The  larger  flaw- 
less plates  are  from  6  to  8  inches  in  diameter. 
The  Minnie  claim,  situated  southwest  of  the  center  of  sec.  35,  T. 
28  N.,  R.  65  W.,  is  also  owned  by  Mr.  Frederick.  The  largest  sheets 
obtainable  on  this  claim  are  8  inches  in  diameter. 
Plates  of  mica  10  inches  across  were  seen  in  a  pegmatite  dike  in 
the  north  center  of  sec.  35,  T.  28  N.,  R.  65  W.  This  dike  is  character- 
ized by  beryl  crystals  4  feet  long.  Plates  of  muscovite  8  inches  in 
diameter  occur  in  a  pegmatite  dike  in  the  center  of  the  SE.  \  sec.  35. 
COMMERCIAL  CONDITIONS. 
The  pegmatite  dikes  in  which  large  sheets  of  mica  occur  vary  in 
width  from  5  to  18  feet  and  carry  from  10  to  15  per  cent  of  muscovite. 
It  is  probable  that  at  least  in  the  four  prospects  described,  muscovite 
is  present  in  commercial  quantities.  There  is  a  marked  variation  in 
the  width  of  the  dikes,  along  both  the  strike  and  the  dip,  and  the  size  of 
the  mica  plates  is  by  no  means  uniform  in  different  portions  of  the 
same  dike.  The  mica  is  clear  and  of  good  quality,  although  varying 
amounts  of  it  are  ruled  and  feldspar,  quartz,  and  tourmaline  occur 
between  the  leaves  of  some  of  the  books. 
Mica  mines  situated  in  the  Western  States  are  operated  at  a  con- 
siderable disadvantage  on  account  of  the  high  freight  rates  to  the 
eastern  market.  A  mine  in  the  Black  Hills,  South  Dakota,  however, 
whose  transportation  facilities  are  comparable  in  a  general  way  to 
those  of  the  prospects  at  the  Hartville  uplift,  has  shipped  mica  to 
Illinois,  apparently  at  a  profit.  High  freight  rates  also  prohibit  the 
utilization  of  feldspar  and  quartz,  common  by-products  of  mica 
mines,  in  the  manufacture  of  pottery.  These  Wyoming  prospects 
would  furnish  a  considerable  percentage  of  sheet  mica  for  the  glazing 
trade.  Although  large  mica  plates  are  in  less  demand  than  formerly 
for  stove  doors,  since  smaller  sheets  are  now  used  in  paneled  doors, 
the  introduction  of  mica  lamp  chimneys  has  perhaps  offset  this 
decrease  in  the  demand.  Smaller  plates  could  be  used  in  making 
composite  sheets  of  mica  called  mica  board  or  micanite,  and  the  waste 
mica  could  be  shipped  for  grinding.  The  mica  of  these  prospects 
would  probably  bring  from  35  to  50  cents  per  pound.  The  Crystal 
Palace  and  Savage  claims  can  readily  be  reached  by  road,  and  the 
mica  can  be  hauled  to  Ironton,  Wyo.,  on  the  Chicago,  Burlington  and 
Quincy  Railroad,  for  $1.25  per  ton.  The  cost  of  transportation  from 
the  New  York  and  Minnie  claims  would  be  somewhat  greater.  It  is 
probable  that  under  careful  management  mica  of  excellent  quality 
could  be  produced  in  the  Haystack  hills  at  a  small  profit. 
