GEOLOGY OF MOUNT MARCV 21 



tacts near Owls Head, which looks like sericite and is believed to oe 

 it. Less abundant than either the garnet or the wollastonite in the 

 specimens collected in pale green diopside. 



The following two analyses of the garnet-wollastonite rock were 

 very kindly made for the writer by Dr G. S. Rogers. No. i is the 

 contact rock, chiefly Vv'ollastonite and garnet, with a little calcite and 

 diopside. A sample much richer in wollastonite is given under no. 2. 

 No. 3, also made by Doctor Rogers, is of nearly pure garnet, from 

 another place along the contact. The analysis yielded also MnO 0.18 

 not mentioned in the tabulation. 



I 2 3 



SiOs 48.17 62.56 36.29 



A1203 12.69 I 2.39 10.29 



Fe^Oa .84 j 15.05 



FeO 1. 41 2.92 



MgO .40 1. 57 .45 



CaO 34.06 28.97 32.85 



Loss 1.78 3.85 1.84 



Sum 



99.3s 



Grossularite 



55-91 



Andradite 



2.58 



Wollastonite 



19.64 



Quartz 



12.48 



Diopside 



4-75 



Calcite 



4.00 



99.34 99.69 



10. 38 45-45 



47.7s 

 37-66 

 34.32 



8.44 



8.73 



Total 99.36 99.53 



In the third analysis, the unassigned per cents are pyroxene, 

 carbonates, water and titanic oxide. They can not be assigned with 

 out assumptions and are at best of small importance. 



The analyses show that the garnet in the first two cases is chiefly 

 the lime-alumina variety, grossularite, and as the other silicates call 

 for no bases beyond the customary amounts in earthy limestones it 

 is quite possible that the original sediment was an earthy limestone 

 which had been recrystallized by the action of the igneous rock 

 without the necessary admixture of other substances from the 

 magma. The substances which have been driven off would be 

 carbonic acid from combination with the lime, magnesia and ferrous 

 iron, and water from combination with the alumina as kaolinite, and 

 with the ferric oxide as limonite. Possibly all the silica was not 

 originally in the form of quartz, but might have been the partially 

 hydrated form chert. If, however, we assume that the silica was all 

 quartz, or chalcedony, and assign the other bases to the above com- 



