Composition:

Petrographic Description:  The sample is a holocrystalline, allotriomorphic 
rock consisting of undulose quartz (34%), coarsely twinned microcline 
(27%), and plagioclase showing albite twinning (36%); the latter are often 
subhedral and frequently have sericitized cores.  Sympletic texture was 
observed in a few areas of the sample.  Minor amounts of biotite are present 
(1.3%) which has often been altered to muscovite plus hematite.  Opaques 
comprise <1% of the rock sample.  There was no sign of calcite in thin 
section, nor was the rock analyzed for CO2, but the spectrum shows weak 
carbonate bands indicating a small amount of calcite (<1%).

Microprobe Analysis:  Microprobe analysis revealed the alkali feldspar 
contained very little sodium (approx. 1% by weight), while the plagioclase 
composition was nearly constant at about An15 (oligoclase).

Chemical Analysis:
SiO2  75.8
CaO  1.39
TiO2  0.03
Na2O  4.31
Al2O3  13.99
K2O  3.55
Fe2O3  0.04
H2O  0.38
FeO  0.30
P2O5  0.0
MnO  0.01
MgO  0.14
TOTAL  99.94
