114 
BAVARIAN BASALTS 
The phenocrysts of the feldspar basalts are the same as in the 
last mentioned group of nephelite basalts, but in some localities 
the titanium aiigite has a green, diopside-like kernel. The ground- 
mass consists of augite, magnetite and plagioclase (labradorite- 
bytownite). This plagioclase occurs in very thin plates, with 
lamellar twinning^ Besides this, there is another more acid 
plagioclase. This forms a mesostasis, like the nephelite in the 
group already mentioned. 
;Nephelite-bearing feldspar basalts are quite similar to the nor¬ 
mal basalts, but with this diiference; the mesostasis instead of 
being an acid feldspar is nephelite. Glass is absent. The pleo- 
chroism of the reddish brown substance is not conspicuous, but 
the refraction and double refraction are about the same as in the 
green substance. Lawson ^ gives to a pseudomorphose similar 
to this one the name Iddingsite, considering it as an original min¬ 
eral of the basalt. Michel-Levy ^ applies the name mineral rouge 
to the reddish-brown substance. Other petrographers speak of it 
as a rusted olivine; but this latter denotation is quite wrong. 
Doubtless both the green, and the reddish-brown substances, are 
silicates, rich in iron and soluble in, and gelatinizing with, cold 
hydrochloric acid. Moreover, their crystal form is that of the 
olivine, and sometimes fresh remnants of this mineral are notice¬ 
able. 
The basalts under consideration contain many inclusions. These 
are subject to careful scrutiny. They are divisable into two 
groups: endogene, or fragments of plutonic rocks, and exogene, 
or fragments of the older rocks lying near the surface. 
Fragments of the plutonic rocks, free from feldspar, are fre¬ 
quently found as inclusions, most of them being peridotites or, 
more properly speaking, Iherzolites, composed of olivine and two 
pyroxenes, a monoclinic and an orthorhombic. The diopsidic py¬ 
roxene is found to have been partly altered into glass by the heat 
of the basalt, while the borders of the enstatite and hypersthene 
have been changed to olivine and diopside. More seldom are 
found fragments of pyroxenite (Websterite). These are com¬ 
posed of hypersthene and diopsidic augite, the lamellae of the first 
being inter-grown with the latter and vice versa. 
Of much wider interest are those inclusions which have been 
2 Bull. Geol. D^pt., University of California, Vol. I, 31 pp., 1893. 
3 Bull. Sec. Geol. de France, 1890, p. 831. 
