PY TT OT TE YIN SOT 
FOS NER ven 
A N:o 1) Igneous Rocks of Sviatoy Noss in Transbaikalia. 67 
epidote in the syenites from Österbotten, Finland 2), and 
in the helsinkites in southern Finland 2). ; 
It may be inferred that the epidote would be an alteration 
product of the other normal constituents of the sviatonossite, 
as anorthite and andradite. To the present writer it seems, 
however, that the epidote has originated instead of them 
rather than from them. There is nothing to indicate that 
the plagioclase should have been originally more anorthitic 
than it is actually. 
A specimen from point 60B shows, in al essentials, 
the same characters as the former, but perthitic feldspar is 
absent and all the potash feldspar is cross-hatched microcline. 
The plagioclase shows, in sections | PM, a parallel extinction, 
thus having the composition Abg,. Asa rule, the crystals 
have much more albitic marginal zones. 
Another specimen from the same point is much richer 
in andradite and epidote than the former ones, and the plagio- 
clase gives in sections | PM extinction angles of + 8 which 
value, together with a refringence considerably higher than 
that of the Canada balsam, points on a mixture of the com- 
position Ab,,. When twinned finely according to the albite 
and pericline laws combined this plagioclase closely resembles 
cross-hatched microcline. No potash feldspar could be 
detected in the section. 
From point 64 B k was collected a specimen composed 
of plagioclase (nearly Abg,), cross-hatched microcline, andra- 
dite, dark bluish green hornblende having its axial plane 
in the plane of symmetry, quartz, epidote with orthite, 
titanite, apatite, magnetite and pyrite. The hornblende 
occurs in poikilitic intergrowth with the quartz, not unlike 
the epidote-quartz-myrmekite that commonly surrounds 
this hornblende-quartz-intergrowth. No pyroxene is present 
here, but it seems clear that these groups of hornblende, 
quartz and epidote have originated instead of the pyroxene. 
1) E. Mäkinen, »Översikt av de prekambriska bildningarna i mellersta 
Österbotten i Finland». Bull. Comm. Geol. Finl. N:o 47 (1916). 
2) A. Laitakari, »Einige Albitepidotgesteine aus Sädfinnland, ibid. N: 0 48 
1918). 
