Mineral Contents of Quartz Rock. 323 



lies at the northern extremity of the same elevation, is much less dis- 

 tinct. But immediately beneath this variety, the rock takes so much 

 mica into its composition as to become slaty, almost mica slate even. 

 (No. 591.) 



In general the dip and direction of the strata of this rock corres- 

 pond to those of the gneiss and mica slate with which it is connected. 

 In Berkshire I have already remarked that the direction is usually 

 north and south., and the dip east, at rather a small angle. At the 

 quarry just mentioned, however, the dip is from 10 to 15 westerly; 

 but the buhrstone dips about as much in the opposite direction. And 

 in the quarry we find veins of granite, indicating the proximity of a 

 larger mass of that rock ; though I did not explore the surrounding 

 region for it : but I think this fact will afford a probable explanation 

 of this anomaly in the dip of the strata. In the northeast part of 

 Windsor, high up the Hoosac range of mountains, this rock dips north 

 about 25. 



The quartz rock in Northfield and Bernardston, west of Connecti- 

 cut river, dips from 20 to 60 east, and runs north and south. East 

 of the river, its dip approaches 90 east. In Southborough its direc- 

 tion is nearly east and west, and its dip northerly and large. In Ox- 

 ford and Webster its direction is nearly north and south and its dip 

 from 20 to 45 west ; though in the west part of Oxford I noticed a 

 dip of 10 easterly, the rock being interstratified with gneiss. In 

 Sutton the dip is from 30 to 35 north, corresponding to that of the 

 gneiss in the vicinity. 



Mineral Contents. 



Scar^ sly any rock in Massachusetts is so destitute of simple mine- 

 rals as this ; unless we include in it those metallic veins of which 

 quartz is the gangue. And these may more appropriately be de- 

 scribed under quartz ; in which rock these veins for the most part oc- 

 cur. Hematite iron ore, forming the cement of the quartzose breccia 

 in Dalton, is the most interesting mineral in the quartz rock. Sul- 

 phuret of iron, also, has been observed in small quantities in that 

 quartz rock which is associated with talcose slate in Hawley, &c. 

 In Pittsfield, Worthington, &c. masses of quartz are found of a yel- 

 lowish color, and appear to be genuine ferruginous quartz. Some- 

 times this quartz passes into yellow jasper, and also into chalcedony 

 and hornstone, as at Dalton. 



