Nepheline-porphyry: Fox Bay type. 
This rock, in a somewhat altered condition, is known 
under the name of gieseckite-porphyry. И is the mother-rock 
of the pseudomorphs called gieseckite which formerly have been 
regarded as a particular mineral. The fresh rock was first 
found by Pıneer 1828. Later, Tamnav, examining Pincer's col- 
lection, found that gieseckite in fresh condition is identical 
with elæolite*. The specimens to be described in the following 
lines have been collected by Dr. Sreenstrup, in 1888. The exact 
locality is on the northern side of a small bay, Fox Bay, at 
Akuliarusek on the Igaliko Fjord. 
Mineralogical characters. — The fresh rock is a porphyry 
with large phenocrysts of nepheline and felspar imbedded in a 
violet- brown, almost dense ground mass. 
The nepheline-phenocrysts are present in large quantities. 
They are short hexagonal prisms showing the combination 
(1010) : (0001) : (1011). The thickness of the prisms averages a 
little more than one centimeter, and the height is about the 
same. The general appearance is that of typical elæolite and 
its colour is green. In some cases an alteration to reddish 
aggregates of muscovite has taken place on the surface of the 
crystals and along cracks. The nepheline contains innumer- 
able minute inclusions, partly fluid-cavities and partly minerals. 
Among the latter the most conspicuous are scales of a green 
biotite and small grains which apparently are egirine, but the 
majority of the inclusions are in such small grains that no 
determination of their nature has been possible. In the central 
portion of each nepheline-crystal the inclusions are evenly 
scattered, in the peripheral portion they show a zonary arrange- 
ment. 
The felspar-phenocrysts are less numerous than the nephe- 
1 H. Rosenpuscu, Mikroskopische Physiographie Il, 1, р. 544 (1907). 
? Poggendorfi’s Annalen der Physik, vol. 43, 1838, р. 149. 
