REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 rlOl 



Exposures of the gneiss with associated bosses of gabbro were 

 found near Deer creek, a mile to the west of Callahan pond, 

 along the western side of the road just south of Irishtown, and 

 on the southeastern spur of Snyder hill. The idiomorphic feld- 

 spar seen under the microscope is labradorite. It is twinned on 

 the albite law in broad lamellae and has the usual clouded habit 

 of the feldspars in gabbro. The single lamellae are filled by 

 innumerable rods and dots irregularly placed, probably magnetite 

 microlites. These are frequently very abundant and of minute 

 size in one lamella and coarser and far less abundant in the suc- 

 ceeding band. Other feldspar inclusions are in the nature of 

 larger, oriented rods, such as would indicate the passage of iron- 

 bearing waters along solution planes. The dark silicates are 

 irregular, clear green masses of hypersthene, and abundant 

 biotite, in red brown shreds, favoring association with grains of 

 magnetite. The rock also carries garnet. 



An interesting phase of the gneiss is found at the point where 

 the road leading to the North Woods club crosses the Boreas 

 river. The feldspar is a reddish pink ortho€laise. This rock ex- 

 tends for over a mile up stream on the western bank of the river. 

 The relation between the gneise and the limestone with its 

 associated schists and hornblendic bands, is not left doubtful, 

 though, in the majority of instances where the rocks outcrop 

 together, the differential effects of metamorphism on the gneiss 

 and on the far more sensitive limestone are such as tend 

 to disguise it. The limestone one and a quarter miles to the 

 east of Huntley pond is exposed conformably interbedded be- 

 tween gneiss and quartzite. A six inch band of limestone is 

 found along the Hudson river a little southeast of Pisgah 

 mountain, regularly bedded with gneiss above and below it. 

 East of Bullhead pond, along the road, gneiss is again found 

 with a bed of limestone, the two exhibiting the same strike 

 and dip. The limestone is exposed with gneiss lying con- 

 formably above it at a point just south of the stream which 

 flows into Jones brook, 2 miles northwest of Olmstedville. 



