THE CHESTER AMPHIBOLITE AND SERPENTINES. 147 



Ul':Si:.MK OF rAllAUENESIS. 



1. Limonite, gibbsite, allopliaue. 



2. Mag-iietite, emery, disssemiuated coruudophilite. 



3. Corundophilite in veius, touriualiue, pyrite, epidote, coniiuUiiii in 

 veins, oligoclase. 



4. Corundophilite in incrustin<^ layers, diuspore, margarite, rutile, 

 epidote, chalcopyrite, menaocanite. 



5. Diaspore, niarg-arite, menaccanite, brookite, calcite. 



6. Specular iron, aragonite, calcite, nialaohite. 



GENERAL EXPLANATION AND CORRELATION OF THE CHESTER AMPHIBOLITE 



SERIES. 



I desire to bring together here the reasons which lead me to conclude 

 that this series was originally a more or less impure ferruginous dolomitic 

 limestone, and to consider also the residual facts which favor the opinion 

 that these rocks were derived from basic and ultrabasic eruptives. 



I have attempted to trace the enstatite-serpentine and the limestone beds 

 of the southern part of the range back from their present to their earliest 

 clearly demonstrable condition, in a series of sections following, which 

 have special application to the newly opened and most interesting quarry 

 of the Westfield Marble Company (see page 92), but which are equally 

 true of all the range north to Blandford. 



ORIGINAL CONDITION OP THE ENSTATITE-SERPENTINE AND LIMESTONE COMPLEX. 



1. The steatitization. — The alteration of the abundant tremolite beds, 

 or those of actinolite which do not contain a large per cent of iron, to talc 

 is common and easily understood. This is the latest change of the beds 

 concerned, except simple solution of the limestones and the coating of 

 fissures with iron rust. 



The fibrous-radiate structure, of nearly all the steatite beds inav be 

 assumed to be proof that they are altered tremoUte and actinolite beds. 



There has often been an intermediate serpentine stage, and serpentine 

 of all kinds has changed into talc. This is sometimes a very modern 

 change. I have observed cases where it was in considerable part post- 

 Glacial. 



2. The serpentinization. — The alteration of the magneslan mineral 

 enstatite, as Avell as of the olivine, ])yroxene, dolomite, and actinolite, into 



