664 NORMAN L. BOWEN 



chlorite and the varying "grain" of the mosaic the original lamination 

 of the sediment is preserved. The feldspar is stained a deep red by 

 tiny flakes of hematite. In a few individual grains albite twinning 

 was discernible and the extinctions combined with the indices deter- 

 mined them as albite. Rarely small garnets are found. 



It is typical adinole of diabase contacts believed to be produced by 

 waters emanating from the diabase. 



The intrusive becomes finer in grain as it approaches the sediment. 

 For about three inches from the contact the diabase has a few "red 

 spots" and these prove to be micrographic intergrowth of quartz 

 and albite. The red color is seen to be due to little flakes of hematite 

 in the feldspar. The plagioclase of the diabase proper has in large 

 part gone over to sericite, and most of the augite to chlorite. Small 

 pink garnets are an important constituent of this micropegmatite and 

 sometimes amount to about lo per cent of its bulk. 



In places a zone of brecciated slate a few inches wide occurs along 

 the contact. The "diabase" filling the spaces between fragments of 

 slate is very rich in this pink micropegmatite (quartz and albite); 

 is indeed sometimes composed almost entirely of it. Obviously the 

 altered sediment has been influential in the production of this grano- 

 phyric material (see Fig. 5). 



About 100 yards south of the point just described, and on the 

 same contact, the diabase has again these "red spots" near its contact 

 and it passes rather abruptly into a reddish feldspathic rock about 5 

 feet thick. This is found under the microscope to consist of large 

 phenocrystic individuals of albite in a ground-mass of quartz, albite, 

 and chlorite. The quartz amounts to about 15 per cent and the 

 chlorite to about 30 per cent, black iron ore about 5 per cent. A very 

 few small garnets are scattered throughout the rock. The albite 

 has again the tiny flakes of hematite, whence the red color. Small 

 areas of very fine micropegmatite are found, showing the beginning of 

 a granophyre structure. The rock has obviously the composition 

 of adinole and passes quite gradually into the reddish-purple adinole 

 which retains the structure of the original sediment. It is merely the 

 more perfectly recrystallized adinole, closer to the intrusive. The 

 granophyric material of special development in the diabase close to its 

 contact has been introduced from the adinole at the time of its forma- 



