442 WARREN AND POWERS DIAMOND HILL-CUMBERLAND DISTRICT 



The massive quartzite is exposed near Albion, on the east side of the 

 Blackstone Eiver, in a long ridge extending parallel to the river. The 

 cuts of the Grand Trunk Railway expose a section from this point to 

 Manville, on the east side of the river. Occasionally bands of greenish 

 gray phyllite occur in the quartzite and furnish a guide to the bedding. 



The quartzite is practically confined to a broad belt along the Black- 

 stone River. A small amount of the same rock occurs northwest of Iron 

 Mine Hill, at the State line. There are a number of outcrops of quartz- 

 ite at this point, with Ashton schists on the east. North of Little Pond 

 are several xenoliths of quartzite of considerable size in Grants Mills 

 granite. 



The phyllite is exposed southeast of Manville, on the east bank of the 

 river, and also in some railroad cuts on the west bank. The rock is 

 usually dark gray in color and thin-bedded, showing abundant mica. 

 The phyllite consists of minute grains of quartz, flakes of muscovite and 

 biotite, and cr3'stals of magnetite. Epidote does not appear to be present 

 in the fresh rock. 



A8HT0N SCHISTS 



The most widespread rock of the entire area is a green to almost black 

 schist which stretches far east of the Blackstone River, inclusions of it 

 being found in the granite of Joes Rock. All the igneous rocks of the 

 area have apparently been intruded partly into this schist and the older 

 ^ Cumberland quartzite, which together formed the '^Grundgebirge'^ of the 

 region. 



The Ashton schist is in the main a greatly sheared and altered chlo- 

 ritic rock, usually thin-bedded and green in color, with abundant epidote 

 developed as nodules and as ramifying veins. Sometimes, however, it is 

 a hornblende schist, a green actinolite schist, or a massive, blackish quartz 

 schist. West of Manville there is a micaceous blue quartz schist asso- 

 ciated with the common green chloritic variety. 



In several places the schist grades into a conglomerate. There is an 

 exposure of the latter a short distance north of the gabbro which outcrops 

 west of Iron Mine Hill. The conglomerate here consists of occasional 

 pebbles of Cumberland quartzite in a green schistose matrix. The peb- 

 bles are, on an average, an inch long and well rounded. The maximum 

 length of the pebbles is 4 inches. The beds strike north 72 degrees west 

 and dip 45 degrees east. Another exposure of conglomerate is found on 

 a hill one mile west of the West Wrentham station, near the contact of 

 the riebeckite granite with the schist. The pebbles here consist largely 

 of a granite which superficially resembles the Milford granite, but which 

 is not now represented in the area. 



