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DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS142.1B, HS142.2B, HS142.3B, HS142.4B
MINERAL_TYPE: Tectosilicate
MINERAL: Andesine (Plagioclase, Feldspar group)
FORMULA: (Na,Ca)Al(Al,Si)Si2O8
FORMULA_HTML: (Na,Ca)Al(Al,Si)Si2O8
COLLECTION_LOCALITY: Montana
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
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.
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
Grain size fractions are indicated by the extension after the sample number:
.1B = <5 µm
.2B = <74 µm
.3B = 74-250 µm
.4B = 250-1200 µm
IMAGE_OF_SAMPLE:
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
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
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem
COMPOSITION_TRACE: None
COMPOSITION_DISCUSSION:
No compositional analyses available
END_COMPOSITION_DISCUSSION.
MICROSCOPIC_EXAMINATION:
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
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
END_SPECTROSCOPIC_DISCUSSION.
SPECTRAL_PURITY: 1c2_3_4_ # HS142.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2_3_4_ # HS142.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2c3c4c # HS142.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2_3_4_ # HS142.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns