444: JPirsson and Washington — Geology of New Hampshire. 



subhedral phenocrysts of alkali feldspar. The rock is grano- 

 phyro-liparase or quartz syenite porphyry. 



Belknap .Dikes and other Occurrences. — On the upper 

 slopes of Mt. Belknap dikes are found of widths varying from 

 a few inches to twenty feet, of branching and anastamosing 

 character. A large one, 20 feet in width, occurs on the 

 shoulder of the west spur of Mt. Gunstock. They are also 

 found as narrow dikelets in the massive rock composing the 

 lower west slopes of Locke's Hill. They are flesh-colored rocks, 

 compact, dense, macrocrystalline, showing occasional, scat- 

 tered phenocrysts of feldspar. Under the microscope they are 

 very fine-grained to almost crypto-crystalline mixtures of 

 quartz and alkali feldspar. In those where the grain is coarser 

 shreds of biotite appear. The feldspar phenocrysts are some- 

 times of oligoclase but mostly alkalic feldspar and oifer 

 nothing of especial interest. In those with the finest grain 

 the material is apt to be arranged in micropoikilitic patches. 

 They are too line for metric analysis, but their whole char- 

 acter and relations are such that we have placed them provis- 

 ionally under liparase, though it is possible that sometimes 

 they are quarfelic instead of quardofelic and should be classed 

 as alaskase. In Rosenbusch's system they would probably be 

 termed quartz-bostonites, especially if their relations and gen- 

 etic associations with the syenite and camptonite be taken 

 into account. 



Other instances are found in dikes cutting outward through 

 the enclosing schists at the west foot of Mt. Gunstock. These 

 are fine-grained, megascopically even granular or homome'tric 

 rocks of pale yellowish to flesh color whose average diameter 

 of grain is about l mm . They evidently belong under this 

 heading and no further description of them is necessary. 

 In the older systems they would be classed as fine-grained 

 granites or aplites. They stand in evident relation with the 

 pegmatitic masses of quartz and feldspar found in the schists at 

 the head of the Gunstock liiver. 



The Breccia Cement. — As already described in the forego- 

 ing part on geology, there is on the lower southwest foot of 

 Locke's Hill a brecciated mass consisting of blocks of various 

 character and of all sizes embedded in a fine-grained aplitic 

 granite intrusion. The study of a number of sections of the 

 latter rock shows that it belongs here in liparase. It is com- 

 posed of alkalic feldspar and of quartz with occasional larger 

 phenocrystic alkalic feldspars, which are mostly alkalic but 

 sometimes oligoclase. Occasional shreds of biotite, grains of 

 iron ore and zircon occur. 



The rock is so like the type analyzed and described and the 

 Gunstock dike that it must be considered as of the same mag- 



