398  CONTRIBUTIONS    TO   ECONOMIC    GEOLOGY,  1905. 
the  southeasternmost  of  these  outlying  strips  of  magnesian  limestone.     It  was  opened  ii 
June,  1905,  and  the  output  to  November  17,  1905,  was  6,000  casks.  The  rock  is  simila 
in  appearance  to  that  from  the  Gay  Farm  quarry.  At  present  it  is  all  burned  for  pulp 
making  purposes.  Its  analysis  is  No.  II  of  the  table  (p.  — )  and  shows  nearly  43  per  cen 
of  magnesia.  A  quarry  formerly  operated  by  Mr.  Geo.  W.  Barry,  on  the  Butler  fai 
about  half  a  mile  south  of  the  quarry  above  mentioned,  is  located  on  the  same  strip 
limestone:  the  rock  is  identical  in  appearance  and  gives  an  almost  identical  analysis. 
the  Dunton  quarry  a  considerable  amount  of  rock  is  rendered  worthless  because  of  tin 
abundant  development  of  talc  (a  silicate  of  magnesium ).  hut  it  remains  to  he  seen  whethJ 
the  quantity  is  sufficient  to  prohibit  profitable  development. 
In  general,  the  exploitation  of  the  isolated  strips  of  limestone  southeast  of  the  mair 
belt  should  proceed  in  a  mosl  cautious  manner,  and  the  following  facts  should  be  kepi 
constantly  in  mind:  First,  the  rock  is  a  magnesian  limestone  which  at  present  finds  a  mar- 
ket only  with  the  pulp  mills:  second,  a  certain  proportion  of  the  rock  is  likely  to  be  talcoa 
and  therefore  commercially  valueless;  third,  the  amount  of  rock  is  relatively  small,  tlu 
hells  seldom  exceeding  200  feet  in  width  and  often  being  less.  They  may  he  expected  tc 
narrow  rather  than  to  widen  with  depth.  The  installation  of  expensive  machinery  is  there- 
fore not   warranted. 
Within  the  broad  Thomaston-Rockland  limestone  belt  magnesian  limestone  was  found 
only  ai  oik  locality,  lis  absence  throughout  most  of  the  belt  is  readily  understood  from 
the  diagram  dig.  lo):  it  is  buried  beneath  the  other  members  of  the  limestone  series. 
Theoretically,  as  is  seen  from  the  diagram,  it  should  come  to  the  surface  on  the  eastern 
border  of  the  belt,  but  tins  holder  is  covered  up  by  clays  throughout  its  whole  length. 
On  the  western  border  of  the  limestone  area,  at  i  he  locality  marked  III  on  the  map,  we  do 
however,  find  a  magnesian  rock.  This  i-  ;li  the  Levensaler  quarry  about  1  mile  north  oi 
Thomaston.  It-  approximate  situation  with  respeel  to  the  rest  of  the  limestone  bell  is 
indicated  by  the  letter  B  ill  fig.  lo.  The  analysis  is  \o.  Ill  of  tin1  table  (p.  — )  and  shows 
21  perc  nt  of  magi)  sia.  B  >sid  ^carrying  this  lower  magnesia  percentage  the  rock  iscoarsa 
and  of  a  bluer  color  than  that  of  the  outlying  area    east  of  the  main  belt. 
The  most  important  deposits  commercially  of  magnesian  rock  are  those  2  miles  north- 
west of  the  village  of  Warren.  Here  there  is  a  down-folded  belt  of  limestone  similar  in 
origin  to  the  magnesian  belts  southwesl  of  Rockland,  but  considerably  wider  and  profl 
ably  deeper.  The  principal  difference  is  in  the  fact  thai  the  schists  which  surround  (under- 
lie) the  limestone  have  been  permeated  with  granite,  dikes  of  which  occasionally  cut  the 
lime-ton:'.  The  jiirsiir-  of  this  granite  has  resulted  in  a  greater  amount  of  recrystalliza- 
tion  and  purification  of  the  limestone  than  in  the  Rockland  region,  but  it  has  also  resulted 
in  the  development .  near  the  granite,  of  silicate  minerals  in  good-sized  crystals,  which  render 
some  of  the  rock  worthless.  For  years  this  rock  has  found  a  ready  market  for  pulp-mill 
use,  about  five-sixths  being  shipped  as  lime  and  one-sixth  as  raw  rock. 
During  the  past  year  the  Warren  Company  has  placed  on  the  market  about  20,000  casks 
of  this  magnesian  lim  ■  for  building  purposes.  On  the  relative  merits  of  the  calcium  and 
magnesian  limes  for  building  purposes  the  following  may  be  quoted  from  Eckel:  a 
The  relative  merits  of  these  two  classes  have  been  frequently  discussed  in  the  text-books  and  technical 
journals  and  are  still  subjects  of  controversy.  The  facts  of  the  case,  however,  seem  to  be  simple  enough 
and  may  be  summarized  as  follows: 
Eigh-caJcium  limes  slake  rapidly  on  the  addition  of  water  and  evolve  much  heat  during  slakina 
'I' hey  also  expand  greatly,  giving  a  large  hulk  of  slaked  lime.  Magnesian  limes  slake  very  slowly  and 
evolve  very  little  heat  during  the  process.  Their  expansion  is  also  less,  so  that,  taking  equal  weights 
thej   give  less  hulk  of  slaked  lime. 
Owing  to  the  slowness  and  coolness  with  which  the  magnesian  limes  slake,  there  is  some  danger  that 
the  average  mortar  mixer  will  not  give  them  sufficient  time  to  slake  thoroughly.  Owing  to  the  fact 
that  they  make  less  bulk  of  slaked  product  than  do  high-calcium  limes,  the  average  contractor  or 
builder  thinks  they  are  too  expensive;  hut,  on  the  other  hand,  they  arc  very  much  stronger  in  long- 
time tests  than  the  high-calcium  limes,  and  will  therefore  carry  much  more  sand. 
a  Eckel,  E.  C,  Cements,  Limes,  and  Plasters,  1905,  p.  115. 
