BOULDERS OF LITCHFIELDITE 465 



SO that the pits, like the associated feldspars, range from 1 centimeter to 

 8 centimeters in length. The content of nephelite is variable, from less 

 than 1 per cent to more than 20 per cent of a boulder. Much less abun- 

 dant are cancrinite and sodalite. The former seldom forms as much as 

 1 or 2 per cent of the rock and appears to fail entirely in most of the 

 boulders when studied with the hand lens. The sodalite is still rarer, 

 constituting isolated grains, narrow veinlets, and schliers. Most of the 

 rock is composed of microcline, microperthite, microcline-microperthite, 

 orthoclase, soda-orthoclase, and a lustrous lepidomelane with strong ple- 

 ochroism in green tintes. Zircon and magnetite are rather rare acces- 

 sories. 



Bayley gives the following analysis of the boulder rock : 



Percent Calculated Composition (Bayley) 



SiOa 60.39 



AI2O3 22.57 



Fe^Os 42 



FeO 2.26 



MnO 08 



MgO 13 



CaO 32 



Na^O 8.44 



K2O 4.77 



H2O 57 



CO2 tr. 



Per cent 



Albite molecule 46.92 



Orthoclase molecule 27 . 01 



Nephelite 17.04 



Biotite « 6.89 



Cancrinite 1 . 99 



99.85 



99.95 



Details as to the chemical analyses and physical properties of the con- 

 stituent minerals may be found in Bayley's paper. « 



LiTCHFIELDITE IN PlACE 



The glacial striae of the region trend south 15° east to south 26° east, 

 with an average trend of south 18° east. Neither in the many stone 

 fences nor in undisturbed morainal deposits were boulders of nephelite 

 syenite found to the northwestward of the broken line X-Y of figure 1. 

 Search for parent ledges was therefore concentrated on the areas showing 

 outcrops south of that line. Two separate bodies of the nephelite syenite 

 in situ were discovered at the points marked with heavy dots, A and B. 

 Since abundant boulders of the same material occur also to the northward 

 and westward of A and B, it is certain that the litchfieldite is in place 

 between the line Joining those points and the line X-Y; but, as shown on 

 the map, that part is quite lacking in outcrops. 



