578 M. AUROUSSEAU AND HENRY S. WASHINGTON 



of the Beemerville, though slightly more silicic. The most note- 

 worthy differences are in the titanium and zirconiimi, and in the 

 ferrous-ferric relationships. The Arkansas syenite apparently 

 contains less of the acmite and more of the diopside molecule than 

 that of Beemerville, and is distinctly poorer in titanium and zir- 

 conium. The minor differences among the volatile constituents also 

 are not without interest. 



THE NEPHELITE PORPHYRY 



The nephehte porphyry, referred to in Kemp's description of 

 the variations of the main mass, is not exposed in a way which 

 permits of a determination of its relationships. It is found in 

 the neighborhood of Mr. T. Conroy's house, near the middle of the 

 main mass, and specimens have been collected from the north of 

 the house, and from the peach orchard southwest of the house. 

 Again quoting from Kemp: 



At the middle of point 4 C on the map the character of the dike changes, as 

 is indicated by the float fragments, for no actual exposures occur. Porphyritic 



facies appear, and an excellent elaeolite porphyry was foxmd Another 



porphyritic rock occurs along this portion of the dike, which lacks the large 

 phenocrysts of elaeolite. It has, however, others of feldspar, and in the slide 

 shows the same tinguaitic base with a much more prismatic development of 

 the elaeolite in the groundmass.^ 



A small dyke of the same rock occurs two miles northwest of the 

 town of Sussex, and is shown on the map of the Franklin Furnace 

 foHo. The nephelite porphyry of the main mass of Beemerville 

 does not reveal its contacts. We believe it to be a dyke of some 

 size, intruding the main mass, and both coarse- (definitely porphy- 

 ritic) and fine-grauied modifications, the latter suggestive of marginal 

 relationship, may be collected north of Mr. Conroy's house. 



The rock is typically porphyritic with nephelite crystals, and 

 occasionally with orthoclase. In one specimen small phenocrysts 

 of blue fluorite are quite visible to the naked eye. The groundmass, 

 which has the typical, dull-green color of the tinguaites, is variable 

 in texture in different specimens, and in the finer-grained variety 

 consists of a mosaic of interlocking grains of orthoclase and nephelite, 

 penetrated by minute aegirites. In the more normal variety the 

 aegirites exist in two generations, those of the groundmass forming 



I J. F. Kemp, Trans. N.Y. Acad. Sci., XI (1892), pp. 66-67. 



