88 J. M. Clements — Study of Contact Metamorphisin. 



either totally absent or else is present merely as an accessory. 

 In the adinoles actinolite is the characteristic constituent. 

 The minor constituents, as a rule, are more uniformly distrib- 

 uted than in the spilosites. However some spots are present 

 and are composed essentially of actinolite. The actinolite is 

 present in sheaf-like growths, lying commonly in an exceedingly 

 fine-grained mass of quartz and albite, with some flakes of 

 chlorite and grains of epidote. The adinole is rendered rather 

 dark by minute black specks which are disseminated through 

 it. In places these are collected in irregular or lenticular heaps. 

 They seem to be carbonaceous matter. 



Analysts of Adinole from Mansfield, Michigan. 



(By Mr. Geo. Steiger, U. S. G. S.) 



Si0 2 74-16 



TiG 2 -37 



A1 2 G 3 _ 11-85 



Fe 2 3 _ -82 



FeO 1-66 



MnO -06 



CaO _.. 2-10 



BaO__ none 



MgO 2-10 



K 2 _ -15 



Na 2 ._. 6-57 



H 2 G at 100°— _ -05 



H 2 Oatl00°+ -52 



PA '08 



C0 2 ._ -09 



C -18 



Total ... 100-76 



Other varieties of the contact rocks. — There is still another 

 kind of contact rock in which actinolite is the chief dark 

 constituent, and in this the actinolite is mainly collected in 

 bands. This rock thus corresponds to the desmosites (banded 

 chlorite rocks) in structure, though differing from them in 

 mineralogical composition. 



The chlorite and actinolite contact rocks may be expected 

 to grade into each other, and such a gradation is shown in one 

 specimen, in which actinolite and chlorite are present in about 

 equal quantity. The actinolite occurs in crystals and sheaves, 

 forming spots ; whereas the main mass of the thin section sur- 

 rounding the spots is formed by chlorite as the dark silicate, 

 associated with feldspar, quartz, and some epidote. 



Comparison of analyses. — From previous determinations in 

 other regions it is well known that the adinoles are next to the 



