Rn, 
lyst. 
DESCRIPTION OF ROCKS AND ANALYSES 31 
2. Basaltoid nephelinite, Wilkitski island, Dr. N. Sahlbom, ana- 
A. Nephelite basanite, Mt. Sverre, Spitsbergen, Prof. Dittrich, 
analyst. ! 
The deviation of this analysis from those of Arctic basalts as 
tabulated by Holmes is still more conspicuous than in the case of 
the Bennet land olivine-trachydolerite. With the young volcanics 
of Woodbay, Spitsbergen, described by Goldschmidt (I. c.), it agrees 
in magnesia content dominating over the lime one, thus being richer 
in mafic minerals; but none of them contains equal quantities of 
alcalies, particularly of potash, which in combination with low silica 
excludes every possibility of feldspar formation. 
Even in this case the classification of the rock offers some diffi- 
culties; the important content of olivine and the low alumina points 
out a basaltic type, as strenghtened by the magmatic symbol, yet 
the intratelluric generation of nephelite together with the perofskite 
(and potash) content without melilite corroborate a nephelinite affi- 
nity, with leucititic dash. From all these rocks the described one 
differs with respect to the magnesia content exceeding the lime, 
having this mark common with the Mt. Sverre-basanite, from which 
it can be derived by raising the alkali content. The rock belongs 
more intimately to the alkali series than any of the Arctic basalts, 
retaining some of the pecularities of this group: it is an Arctic 
basaltoid nephelinite, for which the writer once proposed the name 
, onkilonite “|? 
The mineral composition as given by the norm offers a close 
junction to the true one, differing only in details. The figures of 
Osann significate the rock as belonging to the scarce group, whose 
1 V. M. Goldschmidt, |. c. 
2 H. Backlund, Bull Acad. Imp. Sc. St. Pétersbourg 1915 p. 307. The early 
natives of the north-eastern coast of Siberia, near Behrings sound, called ,onkilon*, 
emigrated, conformable to traditions, under the press of new immigrants, to the 
northern islands in the Arctic ocean. Cf. F. v. Wrangel, Reise, Il, p. 220. Berlin 
1839. 
