No. 6. — Contributions from the Harvard Mineralogical 
Musewm, V1. 
Leucite-Tinguaite from Beemerville, New Jersey. By Joun E. Woxrr.! 
Introductory. 
The post-Cambrian eruptive rocks of Sussex County, New Jersey, have 
been the subject of several interesting papers,” which have described the 
elaeolite-syenite and some of the associated rock masses (ouachitite), and 
several of the dikes, but not the rocks of the whole complex. In 1896 
and other years the writer was engaged with the areal geology of this 
region and made rock collections from the old localities and from several 
new ones discovered in going over the ground ; a list of which with map 
has been published.* He hopes to complete the description of this 
material, of which the present paper forms the first instalment. 
Leucite-Tinguaite. 
This rock occurs as a dike in the main mass of the elaeolite-syenite 
two miles northwest of Beemerville, and near the southwest end of the 
syenite. It was found in a field just under the 1300-foot contour of 
the topographic map and a short distance east of the road over the 
mountain. The dike is fifteen inches wide, cutting coarse syenite, with 
a strike N. 35 W. and dipping 45 northeast ; it is exposed for but a 
few feet. 
The rock has a dull greasy green color, is dense grained and contains 
distinct phenocrysts of nepheline in hexagonal prisms and large pheno- 
erysts of pseudo-leucite, which weather white on the rock surface and 
are greenish white in the fresh rock; they have a diameter of fifteen 
centimeters at the maximum and occur in bands parallel to the walls 
of the dike. Their form is that of the leucite eikositetrahedron, the 
crystal forms rather perfect, and the outlines linear and sharp in cross 
1 Published by permission of the Director of the U. S. Geological Survey. 
2 B. K. Emerson, Amer. Journ. Sci., 23, p. 302 and 376, 1882. J. F. Kemp, 
Amer. Journ. Sci., 38, 1889, p. 130; the same, Trans. N. Y. Acad. Sci., 11, p. 60, 
1892; Amer. Journ. Sci. 45, 1893, p. 298 ; Amer. Journ. Sci., 47, 1894, p. 339. 
8 Geol. Survey N. J. Annual report, 1896, p. 91. 
VOL. XXXVIII. — NO. 6 
