582 M. AU ROUSSEAU AND HENRY S. WASHINGTON 



relations of leucite and orthoclase,^ there is no dij6&culty in accept- 

 ing the leucite tinguaite of Beemerville as the rapidly cooled 

 equivalent of the nephelite syenite. This interpretation also tends 

 to confirm Kemp's diagnosis of leucite in the true differentiates 

 of the magma, the dykes at Rudeville and Hamburg, 



THE OCCURRENCE OF ZIRCONIA AND RARE EARTHS 



In the Beemerville rocks the amount of zirconia is rather high. 

 This illustrates the fact that the region east of the Appalachians, 

 from Essex County Massachusetts, through New Jersey as far as 

 North Carolina, and possibly beyond, is a region rich in zirconia. 

 Numerous localities for zircon have been discovered in New Jersey 

 (personal communication from Dr. J. E. Wolff), and its distribution, 

 and that of the rare earths in places, is so well known in Virginia 

 and North Carohna as to need no great comment here. The 

 zirconia 'is not necessarily confined to sodic rocks, and indeed most 

 frequently occurs in zircon pegmatites, like the well-known peg- 

 matite at Tuxedo, near Hendersonville, North Carolina. The rare 

 earths occur mostly in allanite, which has a fairly wide distribution 

 in Maryland and Virginia. Our determination of the rare earths 

 in the nephelite syenite and nephehte porphyry is the first record 

 of them in northern New Jersey. A number of unpublished 

 analyses of aegirites, by Washington, indicate that the rare earths 

 of the Beemerville rocks occur in the aegirite. The bulk of the rare 

 earth precipitates in our analyses was too small to admit of any 

 separation being made, but the chemical behavior during the 

 deteiminations suggests that yttrium preponderates over cerium, 

 and that thorium is present. 



As the literature of the alkaHc rocks of northern New Jersey 

 is scattered, and in part somewhat old, we append the superior 

 analyses of other rocks of the district, with which we have not 

 dealt directly here. We have included an inferior analysis of the 

 ouachitite of Rutan's Hill, by Kemp, as there is no other chemical 

 information extant concerning the basic lamprophyres. The 

 summation of this analysis is low, in spite of the fact that the iron 

 is all expressed as FeaOj, and the water and CO2 are merely repre- 



' G. W. Morey and N. L. Bowen, Amer. Jour, Sci,, IV (1922), p. i. 



