Sample Description USGS Spectral Library Version 7

USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
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TITLE: Bytownite HS105 Plagio DESCRIPT

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