241 W. S. BAYLEY — SYENITES FROM NEW ENGLAND. 



Occurrence. — As indicated in the title, the rock studied occurs at Red 

 hill, just north of Center harbor, in the town of Moultonboro, Carroll 

 county, New Hampshire. No definite information is available as to the 

 amount of the rock found in this place, but from published descriptions 

 of Red hill it seems likely that the entire eminence is composed of it ; for 

 we read in the "History and Description of New England " :;: that ''tower- 

 ing up some 2,000 feet above the level of the sea is Red hill, formed of a 

 beautiful syenite, in which the feldspar is of a gray-ash color." 



Macroscopic Description. — So few specimens of the rock have been seen 

 that it will be impossible to describe the characteristics of its mass as a 

 whole. We shall have to content ourselves with a rapid survey of the 

 specimens at hand, and with a sufficiently detailed study of their thin 

 sections to prove conclusively that the rock is not a hornblende-syenite 

 as supposed by Hawes, hut is an eleolite-syenite as surmised by Diller. 

 The six slides examined as representing the three types of the rock thus 

 far obtained are. however, so nearly alike in their essential peculiarities 

 that they may evidently be regarded as illustrative of the principal 

 lent are- of the occurrence. 



The specimens furnished by Professor Crosby approach nearer in 

 appearance to some varieties of the Arkansas eleolite-syenites than to any 

 rocks with which the writer is acquainted. They are moderately coarse 

 grained, pinkish-gray crystalline masses, containing irregular patches of 

 an easily cleavable, lustrous, jet black mineral that sometimes measure a 

 quarter of an inch in diameter and sometimes are microscopic in dimen- 

 sions. In the pinkish-gray portion large even surfaces of a twinned feld- 

 spar are easily discernible. These are cross-sections of columnar or 

 tabular crystals, and are the special feature- of the rock that are most 

 prominent. Resides these are scattered here and there dull, irregular 

 masses of eleolite. and occasionally tiny blue areas of sodalite. Neither 

 sodalite nor eleolite is so common as in the litchfieldite, while cancrinite 

 has not been detected in any specimens of the New Hampshire rock. 



The piece in the National Museum corresponds more nearly to Hawes' 

 original description than do the specimens collected more recently. A 

 fragment of it shows a well defined banding, which is due to the flatten- 

 ing of the feldspars and the dark constituents and their arrangement in 

 planes parallel to each other. From the bending of the tlat feldspar 

 plates and the existence of many small fractures crossing them at right 

 angles to their long dimensions it would seem that the platy structure is 

 the result of pressure without much attendant motion. The single thin 

 section examined, however, affords no support to this supposition. 



A third variety of the rock has recently been collected by Mr. M. M. 



♦Coolidge and Mansfield: History an. I Description of New England, vol. I. 1859, p. 585. 



