MINEEALOGY AND PETROGRAPHY.^ 
Petrographical News. — In a recent number of Tscherma¥» 
Mittheilungen'^ Mr. Hyland gives a most interesting and detailed 
account of the lavas of Kilimandjaro, a volcano in eastern equato- 
rial Africa, and of the rocks in its vicinity. Pegmatite, gneiss, am- 
phibolite, basalt-obsidian, limburgite, nepheline- and feldspathic- 
basa'ts, tephrite, basanite, tufas, and other f ragmen tal rocks are 
described. The basalt-obsidian was taken for andesite glass by Bon- 
ney,^ whereas it freally contains no atigite — the mineral regarded 
as augite by Bonney being oHvine. Among the limburgites three 
types are recognized. In one porphyritic olivine predominates over 
augite ; in a second the olivine is subordinate to augite and horn- 
blende ; in the third hornblende is absent and augite is more 
abundant than olivine. The first and second kinds are closely allied 
to the feldspathic basalts, and the third to the nepheline-basalt. The 
olivine in these rocks contains a large number of 
netite, augite, and spinel. Jt is zonally developed and is frequently 
surrounded by a rim of augite needles. The feldspathic basalts em- 
brace hornblendic varieties, in which tlie hornblende is corroded 
and surrounded by an opacitic rim, compos, d of augite, magnetite, 
and olivine, and porphyritic varieties in which the large prophyri- 
tic crystals are anorthite. The nepheline-basanites are especially 
interesting because of the occurrence in them of anorthoclase so well 
developed that Hyland was enabled to determine its optical proper- 
ties with great accuracy. This mineral is undoubtedly triclinic. 
Its extinction on the basal plane varies between 0° and 34°, and on 
the orthopinacoid between 5° and G°. Its specific gravity is 2.63. 
Freed from impurities and analyzed it yielded : 
SiO, AloOg CaO K,0 Na^O HgO 
61.3 28.1 3.02 5.34 7.11 .09 
A leucite basanite contains almost ideally developed leucite crys- 
tals—the first discovered in Africa.^ The other rocks described in 
the paper present no features of especial interest. — An important 
contribution to the study of the younger nepheline rocks has re- 
cently been made by Stock,^ of the University of Leipzig, who has 
thoroughly investigated the material composing the basalt hills 
near Lobau, Saxony. This material comprises nepheline- and 
' Edited by Dr. W. S. Bayley, Colby University, Waterville, Me. 
^ Min. u. Petrog. Mitth., x., p. 203, 
' Report Brit. Ass., 1885. p. 682. 
♦ Cf. Amer. Naturalist, Nov., 1888, p. 1024. 
* Min. u. Petrog. Mitth., ix., p. 429. 
