1 82 EDSON S. BAST IN 



Weathering and shearing effects. — Even those occurrences of the 

 syenite which, in the hand-specimen, appear massive and very fresh, 

 show under the microscope traces of dynamic action and of very 

 considerable weathering. Distinctly, though not highly, schistose 

 phases are even commoner than the massive phases, and are usually 

 much more altered mineralogically. In a few of the less schistose 

 phases considerable pyroxene still remains, but even here some 

 of this mineral has decomposed with the development of horn- 

 blende. In the more schistose phases the femic constituents are 

 green hornblende, fibrous actinolite, and chlorite; in some only 

 chlorite remains. Albite has resisted decomposition much longer 

 than a calcic feldspar would have done under the same conditions. 

 The laths often show fracturing, a pulling apart of the fragments, 

 and their rotation, partial or complete, so that their longer axes 

 lie in the plane of the schistosity. The rotation of the feldspars 

 contributes to the development of the schistose structure, which, 

 however, is due primarily to the distribution of the chlorite in long 

 irregular bands, to some parallelism among the shreds of fibrous 

 hornblende, and to the distribution of secondary epidote grains 

 in irregular aggregates which are elongate palallel to the bands 

 of chlorite. Occasionally some muscovite is developed and aids 

 in defining the schistosity. Magnetite is usually largely altered 

 to titanite or leucoxene. Zoisite, calcite, apatite, biotite, and chlo- 

 ritoid minerals are minor secondary constituents which are some- 

 times present. Very rarely serpentine has been abundantly devel- 

 oped, as in the intrusive mass which forms the 8o-foot hill just east 

 of the steamboat landing at Eggemoggin on Little Deer Isle. 



So far as the writer 's knowledge goes, all of the pyroxene-syenites 

 thus far described which have contained albite have also contained 

 nephelite or some calcic feldspar, and in most cases the albite has 

 been a very subordinate constituent. The rock here described 

 is unusual in the abundant association of the non-calcic feldspar, 

 albite, with the calcic mineral, pyroxene. In the absence of suffi- 

 cient material from localities where the rock was freshest, no chemi- 

 cal analyses could be made, and without such it would be unsafe 

 to attempt an explanation of this association. It may be suggested, 

 however, that the explanation may lie in a deficiency of alumina. 



