MINERALOGICAL NOTES. 147 



gion. That it was the first formed rock in this series is 

 evident for it is cut by the micro-dykes and masses of 

 granite, diorite, gabbro-diorites, the typical eleeolite-zir- 

 con-syenite, micro-syenite veins and quartz porphyries. 

 In a cutting of the Boston and Maine railroad, through 

 the typical diorite of the region, I have detected a large 

 fragment of this basic elseolite rock as an inclusion. 



TYPICAL EL^OLITE-SYENITE. 



In any outcrop of the typical elseolite-zircon-syenite 

 forms will be found in the rock mass which are clearly 

 due to local variation. The type is a coarse feldspathic 

 rock in which the elgeolite and sodalite are seen in large 

 blebs and patches with numerous macroscopic zircon 

 crystals, some of which are one-fourth of an inch long, 

 with perfect double pyramidal faces. In thin section, 

 studied with the microscope in polarized light, the feld- 

 spars are seen to be composed : first, of large irregular 

 crystalline mtergrowths of microcline and albite, and 

 second, areas of orthoclase and occasional crystals of well- 

 twinned plagioclase which is probably labradorite. The 

 orthoclase is often filled with microliths of a dust-like 

 character. In close proximity to the zircons, rhombic 

 sections are often seen of a mineral of a yellowish green 

 color which is isotropic, as yet undetermined. There are 

 also occasional crystals and grains of segirine which show 

 a plechroism varying from blue green to a yellowish green, 

 and, with the quartz wedge as determined by the negative 

 bisectrix makes an angle of 4 or 5 with the vertical axis, 

 some augite which shows brilliant colors in the basal sec- 

 tion, brown hornblende, much perfectly red biotite and 

 some magnetite. In the microscopic investigation of loose 

 grains, the specific gravity of the minerals of the crushed 

 rock, as passed through the 90 sieve and separated in the 



