SP pM 22 FTSE SR ft 
+ 
TV 
SUP TI 
. A N:o 1) Igneous Rocks of Sviatoy Noss in Transbaikalia. 32 
Within the area of mixed rocks on the southwestern shore 
of the peninsula pegmatites also occur, though not in any 
great frequency. The rock is composed almost exclusively of 
potash feldspar and quartz, often in graphic intergrowth, 
and with irregular lumps of magnetite, which seems to be 
a regular constituent of the pegmatites in this part of blie 
peninsula. 
Near topogr. point 7 a limestone mass is penetrated by 
numerous dikes of aplitic pegmatite at whose contacts a 
wall of contact minerals has been developed. Nearest to the 
pegmatite occurs a zone of dark hornblende and thereafter 
another zone of light green or nearly colourless diopside in 
contact with the limestone. Around this compact wall of 
the lime-silicate minerals a zone of limestone is still impreg- 
nated with numerous rounded grains of the pyroxene. At 
places there is, between the pegmatite and the hornblende 
zone, a third compact zone of scapolite. In part the pegma- 
tite dikes are very narrow, being nevertheless surrounded 
by exomorphous contact zones of a considerable thickness, 
often thicker than the pegmatites themselves. And where 
the dikes taper out, their continuation is formed by fissures 
which are still surrounded by the same contact zones, the 
scapolite wall forming their central part. The pegmatite 
dikes have thus graded over into scapolite dikes. This 
phenomenon gives clear evidence of iron- and magnesium- 
silicates being transferred from a magma to its country-rock, 
as is postulated e. g. by the theory of the skarn formation 
in limestones by the influence of the granite magma. Such 
contact walls are, however, of quite an exceptional occur- 
rence. By far the greater part of the pegmatite dikes inter- 
secting limestones have sharp boundary lines without any: 
contact minerals whatever. 
At point 7, near the above-named occurrence of scapolite, 
the limestone encloses pyroxene in the form of large lumps, 
the structure of the pyroxene mass as well as the character 
of the mineral, which is a nearly colourless diopside, being 
quite the same as in that occurring at the contact wall of 
the pegmatite dikes. More irregularly formed inclusions occur 
