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(For further information on spectrsocopy, see:
http://speclab.cr.usgs.gov)
TITLE: Bytownite HS105 Plagioclase DESCRIPT
DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS105
MINERAL_TYPE: Tectosilicate
MINERAL: Bytownite (Plagioclase)(Feldspar group)
FORMULA: (NaAlSi,CaAl2)Si2O8
FORMULA_HTML: (NaAlSi,CaAl2)Si2O8
COLLECTION_LOCALITY: Essex County, New York
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
Part of the albite-anorthite solid solution series.
Sieve interval 74 - 250µm.
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
40 kV - 30 mA, 6.5-9.5 keV
File: labrd105.mdi
References: Borg and Smith (1969); Kroll (1983); PDF2 #41-1486, 19-0926
Found: Plagioclase feldspar, probably intermediate composition
Comments: Peaks are moderately sharp peaks but show poorly resolved alpha1-alpha2
components, perhaps due to some variation in composition or structural state.
Line-based search-match returns 10 plagioclase feldspars in the first 10 hits; the
most likely hit (and only feldspar) from profile-based search-match is #41-1481,
diordered An83Ab17 (bytownite). The delta 2 theta(131)-(1-31)=1.82 degrees and
corresponds to low plagioclase (or intermediate albite) structural state and
composition less than 53% anorthite component (Kroll, 1983, fig. 12). Reflections diagnostic
of low plagioclase composition (Kroll, 1983, p. 328-9) yield Si/Al=1.3:1 (bytownite
composition). There were unindexed reflections: 8.55 angstroms (weak) is observed
in other patterns and may be instrumental in origin; 4.23 angstroms (very weak)
could be explained by a trace of K-feldspar; and 1.829 angstroms (moderately weak)
remains unexplained.
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
COMPOSITION_TRACE:
None
COMPOSITION_DISCUSSION:
Hunt and Salisbury originally considered this sample to be a labradorite.
END_COMPOSITION_DISCUSSION.
MICROSCOPIC_EXAMINATION:
Not done yet
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
END_SPECTROSCOPIC_DISCUSSION.
SPECTRAL_PURITY: 1b2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
| LIB_SPECTRA_HED: | where | Wave Range | Av_Rs_Pwr | Comment |
|---|---|---|---|---|
| LIB_SPECTRA: | splib04a r 2685 | 0.2-3.0µm | 200 | g.s.= |
| LIB_SPECTRA: | splib05a r 1451 | 0.2-3.0µm | 200 | g.s.= |
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