Name: Augite-hypersthene Andesite
Type: rock
Class: Igneous
Subclass: Intermediate
Particle Size: Solid
Sample No.: Andesite_H2
Owner: JHU
Wavelength Range: All
Origin: Saipan, via Smithsonian (Cat. No
Collection Date: N/A
Description: The sample consists of a dark gray, fine-grained groundmass, with yellow (hypersthene?), dark green (augite?) and white (plagioclase) phenocrysts. The sample is also slightly vuggy. Original ASTER Spectral Library name was jhu.becknic.rock.igneous.intermediate.solid.andesi2.spectrum.txt
Composition:

Petrographic Description:  The modes of phenocrysts gave 30.05% 
plagioclase, 9.8% hypersthene, 3.10% augite, 1.65% magnetite, and 56.30% 
groundmass.  There was no sign of carbonate in thin section, but chemical 
analysis showed CO2 (see below) and the spectrum also shows weak 
carbonate bands.

Microprobe Analysis:  The composition of the augite phenocrysts was W0 
38%, En 38%, Fs 24%, that for hypersthene gave En 64%, Fs 36%.  The 
average composition of plagioclase phenocrysts ranged from An55 to An58 
(labradorite).

Chemical Analysis:
SiO2  -  57.38
CaO  8.48
TiO2  0.62
Na2O  2.76
Al2O3  18.36
K2O  0.74
Fe2O3  4.88
H2O  1.30
FeO  2.26
P2O5  0.02
MnO  0.07
CO2  0.57
MgO  2.40
TOTAL  99.84
