DIOEITE AND GARNET-BIOTITE-NOUITE. 



345 



An analysis of this rock from opposite a house of gothic architecture 

 east of Leverett is given below. It was made by Mr. L. Gr. Eakins: 



Analysis of diorite from Leverett. 



SiO; 



TiO, 



AI2O3 



Fe,Or, 



FeO. 



MnO 



BaO 



CaO 



MgO 



K:0. 



Na..O 



H;0. 

 PiOs 



Per cent. 



51.56 



1.97 



14.82 



4.30 



7.21 



trace 



trace 



7.09 



7.36 



.17 



4.21 



1.47 



.09 



100. 25 



A wholly exceptional band of diorite occurs at the top of the whetstone 

 in the hill west of A. Adams's, m the south of Leverett, and is continued to 

 the west of the north end of the " Flat Hills " road in the northeast corner 

 of Amherst. It is here, in a bed 325 feet wide, a dark, tough, massive 

 diorite, much decomposed and associated with siliceous limestone. 



Some of the amphibolites described in Chapter X as of doubtful orig-in 

 may be altered diabases or diorites, and thus belong here. 



GARXET-BIOTITK-NORITE. 



The rock appears in a single isolated outcrop in the roadside near 

 Gr. Pefifer's house, in the village of Parksville, in Brimfield. It is a fresh, 

 dark olive-green rock of granitic texture and slightly above medium g-rain. 

 Large grains of deep-red garnet are quite abundant, and here and there 

 a group of black biotite scales appears, often crumpled. Many shining 

 cleavage surfaces of the feldspar occur which do not show striation, though 

 the microscope shows all or nearly all of these grains to be multiple- 

 twinned. 



The microscope shows the field to be almost wholly made up of a coarse, 

 entirely fresh mosaic of xenomorphic and equidimensional feldspar, which 

 has all the optical ^Ji'operties of a labradorite (Ali Aiij), with broad twinning 



