1235 
are often accumulated; sometimes they are found together with 
plagioclase- and larger ore crystals. Where the pyroxenes are con- 
tiguous to groundmass they are commonly encircled by a narrow 
zone of ore, which is lacking where they are in contact with 
plagioclases. Apparently this is a chemical exchange between the 
phenocrysts of pyroxene and the still liquid part of the enclosing 
magma. In some samples of the dome resorbed brown amphiboles 
were found; however, they exhibited no idiomorphous erystalform 
and we venture to assume that they are not crystals formed in the 
dome but fragments transported by tbe rising magma. Some of them 
may be fragments of the same crystallization products, from which 
the amphibole-rich homoeogeneous xenoliths originate. 
The groundmass of the dome-roek is rich in glass and contains 
lath-shaped plagioclase and grains or skeleton-shaped individuals of ore, 
while pyroxene has not (or only to a small degree) crystallized in 
this ground-mass. 
The «xenoliths of the domerock. 
Among them we distinguish the following types: 
1. medium-grained, occasionally porphyric xenoliths, consisting of 
plagioclase and amphibole with a small quantity of a more or less 
devitrified glass. 
2. medium-, to coarse-grained xenoliths, made up of plagioclase, 
amphibole with little pyroxene and sometimes a little olivine. Glass 
occurs also in these xenoliths. 
3. medium-, to coarse-grained, sometimes porphyric xenoliths with 
plagioclase, (little olivine), amphibole and much augite and hyper- 
sthene. The olivine was seen ouly in some xenoliths, ore sometimes 
occurs in a small quantity outside the resorption-rims of the amphibole. 
The relative quantity of amphibole, augite, aud hypersthene is variable. 
All xenoliths, in which the number of pyroxenes is not very small, 
have been included here. Glass with microlites was observed only 
in some xenolith and in a very small quantity. 
4. porphyric xenoliths with phenocrysts of plagioclase in a fine- 
grained groundmass in two generations with plagioclase, pyroxene 
and ore. Larger pyroxene-crystals do not occur in the xenoliths, but 
are accumulated in a small marginal zone against the enclosing rock. 
D. fine-grained xenoliths, made up of plagioclase, augite, hyper- 
sthene and little ore. Much glass with microlites is found in some 
samples between the other minerals. 
6. xenoliths of older andesites, some of them bearing amphibole, 
others devoid of amphibole. 
