302 J. F. Kemp — Basic Dike near Hamburg, N. J. 



was based, contained no trace of the spheroids, and that they 

 first appeared in the fresher material of this later discovered 

 and hitherto undescribed dike — which were shared with Mr. 

 Derby. Dr. Hnssak calls the rock a lencite-tephrite and adopts 

 the view originally taken by Mr. Derby. I have since dis- 

 covered the same spheroids in some material from the dike in 

 the Buckwheat Mine at Franklin Furnace, but with different 

 mineralogical contents as will be noted later. Inasmuch as the 

 existence or probable existence of so rare and interesting a 

 mineral as leucite in association with the Beemerville elfeolite- 

 syenite is an important question, some especial care and delibera- 

 tion have been exercised in investigating the rock. 



As opposed to the leucite interpretation, Professor Rosen- 

 busch, in a personal letter, remarks the perfect analogy which 

 the spheroids have with certain others which characterize the 

 " Kugel-minettes." As is well-known to petrographers, the 

 lamprophyric dikes, that contain especially biotite, orthoclase 

 and some plagioclase and that are called minettes, show a 

 marked tendency to develop in certain cases spheroids or 

 " kugeln." Such have been noted by Cohen* from Odenwald, 

 by Linckf from Weissenberg, and by Liebe and Zimmermann^: 

 from Thuringia. Very nearly, if not quite, the same thing is 

 figured by Teall,§ in a rock from the island of Car Craig, near 

 Inchcolm, in the Frith of Forth. The rock itself is described 

 as related to the teschenites, a description that fits the Hamburg 

 dike, perfectly. The rocks described by Liebe and Zimmer- 

 mann are the only ones of the German references of great inter- 

 est here. Some spheroids (kugeln) they regarded as variolitic 

 or perlitic structures, while others, that, like those of the Ham- 

 burg dike, possessed tangential veins of biotite, they rightly 

 inferred could have had neither an amygdaloidal nor a varioli- 

 tic origin. These latter spheroids were formed of crystals of 

 feldspar irregularly grouped. 



In the Hamburg dike the spheroids consist chiefly of anal- 

 cite. This is illustrated in figure 3, in which nearly the whole 

 is of this mineral. The analcite shows at times the faint cubi- 

 cal cleavage, as is indicated, and again it lacks it. The sub- 

 stance is identical with the general groundmass of the rock. 

 A few minute specks of magnetite were in it, and one feldspar 

 rod. In the upper portion a piece of analcite appeared to have 

 suffered a further alteration to a brightly refracting rim of cal- 

 cite and other small clots of the same mineral are seen through- 

 out the spheroid. In other spheroids than the one drawn, 



*Xeues Jahrbuch, 1879, p. 858. 



fldem. 1884, ii, 194. The reference is a review of the original, by H. Rosen- 

 busch. 



% Jahrbuch d. k. Pr. Landesanstalt. 1885, 178-190, but especially 184. 

 § British Petrography, p. 191. Plate xxii, fig. 1 . 



