224 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



of such size and arniiigeinent tluit, on weathering, the rock presents very 

 closely the appearance of a scolitlms sandstone, and I tried for a long time 

 to persuade myself that this was the case. I am now inclined to connect 

 these beds with the beds of tough hornblende rock carrying black garnet 

 which appear in the Conway schists, either alone or as a selvage to the beds 

 of l)lack limestone, as both have the same composition — quartz, garnet, 

 hornblende, and graphite. The hornblende changes often to serpentine. 



A very similar rock appears on the eastern border of the tonalite in 

 Hatfield (near the house of J. Glasner), and is probably a product of the 

 contact action of the latter upon a limestone bed of the Conway schist. The 

 exposixres are not sufficient to make its relations clear. 



Correlation of Amherst schist. — As a feldspathic mica-schist the rock 

 resembles the feldspathic varieties of the Conway schist on the west side of 

 the valley, especially in its southern extension, as about Russell. In this 

 assignment I have been influenced by stratigraphical considerations, by 

 the very general content of graphite, by the common traces of calcite, 

 bv the probable derivation of the eclogite-like rock from bands of arena- 

 ceous limestone like those conuuon in the calciferous mica-schist, and by the 

 fact that these Amherst schists closely resemble the calcifei'ous mica-schist 

 immediately opposite, in Williamsburg, where it is most influenced by 

 the granite and develops into a fibrolite-schist like the neighboring bands 

 of the same schists on the east. 



Minerals in the Amherst schists. — Apart from the barvta-lead veins, 

 described under mineral veins in Chapter XIV, there have occurred the 

 following minerals in the schists: 



(1) Essonite and graphite; west slope of Mount Warner. 



(2) Heulandite in perfect, deep-red crystals, with rosettes of a rewly 

 formed pyrite; head of Prospect street, Amherst, and at the college grove 

 well with pyrophyllite. oo P x (010), — 2 P 5b (201), 2 P oc (201), P 

 (001), 00 P (110). 



(3) Pyrophyllite after feldspar, fibrolite, and biotite. 



In a well at the northwest corner of the college grove the rock was 

 a biotite-schist, much impregnated with granite, which swells to lenses of 

 the coarsest pegmatite many feet in length. Associated with these granite 

 lenses are layers and large masses, which often run off into veins across the 

 schists, of a granitoid mixture of quartz, little feldspar, and much green biotite 



