(For further information on spectrsocopy, see:
TITLE: Andesine HS142 Plagioclase DESCRIPT
MINERAL: Andesine (Plagioclase)(Feldspar group)
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
Andesine is a plagioclase feldspar series mineral whose end members are albite (Na) and anorthite (Ca). Andesine falls into the 30-50% anorthite category in this series.
This sample is a mixture of different phases and was labeled andesine porphyry. The mineral mode confirms this. Average grain size is 40um. This sample could benefit from magnetic separation.
74-250µm sieve interval.
The spectrum indicates a weak absorption band near 2.2-2.3 µm, apparently due to trace alteration not detected by other methods. Roger N. Clark
40 kV - 30 mA, 6.5-9.5 keV
File: andes142.mdi, *.out; ands142b.mdi, *.out (smear mount on quartz plate)
References: Huebner's reference patterns
Found: Plagioclase, K-feldspar, quartz, trace of orthopyroxene
Comment: The feldspars were deciphered using patterns for low albite (WAR-0612) and microcline (Felix Chayes' 37A15). All peaks are very sharp indicating a high degree of crystallinity and compositional homogeneity. The two feldspar patterns are distinct.
J.S. Huebner, J. Pickrell, T. Schaefer, written communication 1994
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
No compositional analyses available
Optical examination gives the following mineral mode:
66 vol% andesine
25 vol% quartz
8 vol% altered andesine (Fe-stained)
1 vol% hornblende
avg. grain size plag = 290µm
avg. grain size qtz = 270µm
avg. grain size populations = 285µm
This sample is a mixture of different phases and was labeled andesine porphyry. The mineral mode confirms this. This sample could benefit from magnetic separation. Plagioclase has low relief and synthetic twining. G. Swayze
SPECTRAL_PURITY: 1c2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
|LIB_SPECTRA:||splib04a r 356||0.2-3.0µm||200||g.s.=|
|LIB_SPECTRA:||splib05a r 961||0.2-3.0µm||200||g.s.=|
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