Composition:

Petrographic Description:  An inequigranular hypidiomorphic rock 
consisting of larger plagioclase euhedra, smaller interstitial alkali feldspar 
and quartz, colorless to pale green pyroxene anhedra which may be partly 
uralitized, and scattered biotite and opaques.  The feldspar is often 
sericitized, and the plagioclase occasionally shows both albite and Carlsbad 
twinning, as well as oscillatory (less commonly gradational) zoning.  The 
average modes are: 70% feldspar, 18% quartz, 8.2% pyroxene, 2% opaques 
and 1.2% biotite.  No carbonate was seen in thin section, but a weak 
carbonate feature near 4.0 microns indicates the presence of a very small (< 
1%) amount.

Microprobe Analysis:  The plagioclase phases proved to be either andesine 
(approx. An47), or a mixture of alkali feldspar (Or55) and plagioclase 
(approx. An39); one feldspar probed was orthoclase (approx. Or97).  The 
pyroxene was augite, or possibly augite with uralite.  Magnetite had from 0.5 
to 1.5 % variation in titania.

Chemical Analysis:
SiO2  61.42
CaO  4.13
TiO2  0.77
Na2O  3.48
Al2O3  15.95
K2O  4.17
Fe2O3  3.6
H2O  1.37
FeO  2.84
P2O5  0.25
MnO  0.11
MgO  2.32
TOTAL  100.41
