MICROPEGMATITE AT CHAPEL HILL. 
BY H. N. EATON. 
During the course of an investigation of the Chapel Hill granites 
now in progress an occurrence of micropegmatite was discovered 
which seems worthy of special mention. The binary granites 
were found to contain micrographic intergrowths of quartz and 
feldspar. The one showing the best development of this pheno- 
menon is described below . 
This rock occurs in a slightly weathered condition just beyond 
the village limits on the slope of the hill along the Hillsboro road 
and south of Bolin’s Creek. Its extent and relation to the other 
rocks of the igneous complex of the region are unknown . 
In handspecimen, the rock is grayish pink in color, and fine 
grained. No hint of the arrangement of the minerals is given 
from a freshly broken surface owing the uniform fineness of grain. 
In thin section, the mineral content is seen to comprise plagio- 
clase, orthoclase, microcline, and some accessory magnetite. The 
striking feature of the slide is the arrangement of the quartz and 
alkali feldspar in the micropegmatitie relation. 
With the exception of the magnetite, plagioclase was the first 
mineral to crystallize. It occurs sparingly in short, stout prisms, 
for the most part idiomorphic, but in places showing absorption by 
the later formed minerals. Twinning occurs after both the carls- 
bad and aibite laws. Owing to strong kaolinization the albite 
striations are frequently difficult to recognize. The maximum 
extinction angle noted was 13 degrees, thus placing the species 
between oligoclase and andesine, and nearer the latter of the two. 
Quartz and alkali feldspar occur mutually inclosing and inter- 
penetrating each other in micrographic intergrowths. The 
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