DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS105.1B, HS105.2B, HS105.3B, HS105.4B, HS105.6
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.
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
.6 = cut slab
IMAGE_OF_SAMPLE:
NO PHOTO
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,
disordered 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, EPMA, 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_ # Bytownite HS105.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # Bytownite HS105.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2b3b4b # Bytownite HS105.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # Bytownite HS105.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # Bytownite HS105.6 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns