64 Pentti Eskola. — (EXIT 
This »aplitic» sviatonossite is not such a well defined type 
as the former, and the description and chemical analysis is 
hardly valid for other than only that occurrence from which 
the analyzed specimen was taken. We shall therefore briefly 
describe a few different specimens as examples, beginning 
with the one used for the analysis. 
The rock consists chiefly of a granular fel d spar mass 5 q 
which is structurally similar to the ground-mass of the por- 
phyritic varieties described on previous pages. There are, 
however, larger grains of potash feldspar also, but these are 
not much larger than the ground-mass individuals, and they 
do not contain such large amounts of plagioclase in perthitic 
intergrowth. The borders are richest in the plagioclase, and 
the intergrowth shows the same kind of structure, much 
resembling graphic intergrowths, as was found in the por- 
phyritic varieties. The inner parts, however, are almost 
destitute of plagioclase laths. ; 
The granular potash feldspar is in part microcline, in 
part orthoclase — at least it has seemingly a parallel extinc- 
tion in the symmetrical zone. There are but. slight traces 
of plagioclase in perthitic intergrowth with this potash 
feldspar. 
The plagioclase is thoroughly granular and does 
not show any crystallographic contours, the structure being 
typically aplitic. In sections | PM I measured the extinc- 
tion angle of + 2”, corresponding to the composition Ab,g. 
Many grains have border zones showing different extinction, 
the angle at first diminishing and, having passed the zero, 
again enlarging with the opposite sign. 
According to the calculated mode the plagioclase of the 
rock should have the mean composition of Abrg. 
The andradite occurs as irregular minute grains, 
often clustered together, accompanied by the pyroxene, 
apatite and titanite. Products of alteration are more common 
than in the porphyritic varieties. In other respects the garnet 
is perfectly similar in both rocks. 
The pyroxene is aegirite-augite having the same 
properties as in the variety described formerly. Itis present 
