1890.] Mineralogy and Petrography. 773 
‘The quartz fragments are surrounded by zones of colorless glass con- 
taining augite microlites, which are in turn surrounded by zones of 
brown glass enclosing microlites and crystals of augite and granules of 
magnetite. According to Vénukoff,* basalts play an important role 
in the geology of Mongolia. They consist principally of feldspar, 
augite, olivine, ilmenite, and magnetite. e feldspar is usually in 
but one generation. When in two, the phenocrysts are anorthite and 
the microlites labradorite. The augite is usually in two generations, 
the larger crystals being violet in color, while the smaller ones are 
green. In some cases the porphyritic augites are made up of an 
aggregate of small grains grouped in such a way as to present the out- 
line of crystals. These aggregates are sometimes surrounded by a rim 
of grains of the second consolidation. Between the minerals above 
mentioned there is often a little of an amorphous base containing 
globulites and microlites, The quartz of an inclusion of granite in 
this basalt is surrounded by a zone composed of augite and small, 
light-colored microlites. The biotite of the granite has been trans- 
formed into a granular mass of magnetite, quartz, and a light brown 
opaque substance. Around it is often a zone of augite grains. Around 
the feldspar the basalt paste becomes light colored, the crystal com- 
ponents are more rare, and in their places are various microlites. 
"Within this is a band of augite microlites, and within this band, imme- 
diately surrounding the feldspar, is a zone of colorless glas. The 
feldspar itself is much fractured. The greenstones® of Wicklow, 
Ireland, occur in intrusive sheets and dykes. They are quartz-mica- 
diorites (composed of quartz, plagioclase, orthoclase, biotite, horn- 
blende, and a little malacolite, chlorite, and apatite), quartz-diorites, 
diorites, augite-diorites (consisting of plagioclase and grains and 
crystals of sahlite or malacolite), diabases, epidiorites, chlorite-schists 
(produced by dynamic metamorphism from diabase), and serpentines, 
derived from diabases. Mr. Somervail 5 regards the gabbros, green- 
‘stones, granulites, and hornblende-schists of the Lizard, Eng., as parts 
of the same rock-mass, the latter-named rocks, according to him, 
having originated from the former by pressure, ——Mr. Marstens? 
gives us a very brief description of diabases and diabase porphyrite 
from among the Triassic traps of Nova Scotia ——-A few dykes® 
3 Ib., p. 340. 
* Proc. verb. soc. Bélg. de Géol., II., 1888, p. 441. 
5 Geol. Magazine, 1889, p. 261. 
— "Amer. Geol., Mch. 1890, p. 140. 
3 Darton and Diller. Amer. Jour. Sci., Apr. 1890, p. 269. 
