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(For further information on spectroscopy, see:
http://speclab.cr.usgs.gov)
TITLE: Nepheline HS19 DESCRIPT
DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS19
MINERAL_TYPE: Tectosilicate
MINERAL: Nepheline (Nepheline group)
FORMULA: (Na,K)AlSiO4
FORMULA_HTML: (Na,K)AlSiO4
COLLECTION_LOCALITY: Bancroft, Ontario
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
"S-13. Nepheline. Bancroft, Ontario (19). This sodium-potassium aluminum silicate, (Na,K)(Al,Si)2O4, is found in igneous rocks whose magmas contained insufficient silica to combine with the soda present to form feldspar. This nepheline sample illustrates very clearly the effect of grinder steel contamination. Note that the two contaminated finer particle size fractions have both reduced reflectivity and their near-infrared bands eliminated. In contrast, the uppermost curve of uncontaminated 0.5µ nepheline is both highly reflective and retains its spectral features. The bands near 1.4, 1.9 and 2.5µ are due to water, presumably present as fluid inclusions in microscopic vesicles within the nepheline. The water is not present as part of the nepheline lattice, and the only contaminant (a very small amount of biotite) would not produce these bands."
Sieve interval 74 - 250µm.
Hunt, G.R., J.W. Salisbury, 1970, Visible and near-infrared spectra of minerals and rocks: I. Silicate minerals. Modern Geology, v. 1, p. 283-300.
IMAGE_OF_SAMPLE:
NO PHOTO
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
40 kV - 30 mA, 6.5-9.5 keV
Files: nephlin19.out, -.mdi, fine (.1B) fraction, ground once;
nephl19b.*, fine fraction not ground; nephl19c.*, 70-250 micrometer
fraction (.3) ground once
References: Borg and Smith (1969) for nepheline; JCPDS 25-776 and
24-176 (cancrinite), 37-476 (sodalite); Huebner's reference
patterns; Deer and others (1963, vol. 4)
Found: Nepheline with Na/(Na+K)= approximate 0.75, trace phlogopite; traces
of cancrinite (probable), sodalite (possible).
Comment: HS-19.3 gives an exceptionally well-crystallized pattern. Unindexed reflections at 5.64, 4.03, 3.44, 2.94, and 2.81 may prove to be nepheline peaks that are too weak to be reported in the literature.
J.S.Huebner, J. Pickrell, T. Schaefer, written communication 1994
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
COMPOSITION_TRACE: None
COMPOSITION_DISCUSSION:
None
END_COMPOSITION_DISCUSSION.
MICROSCOPIC_EXAMINATION:
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
END_SPECTROSCOPIC_DISCUSSION.
SPECTRAL_PURITY: 1c2b3c4_ # 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 3451 | 0.2-3.0µm | 200 | g.s.= |
| LIB_SPECTRA: | splib05a r 4915 | 0.2-3.0µm | 200 | g.s.= |
| LIB_SPECTRA: | splib06a r 15772 | g.s.= | ||
| LIB_SPECTRA: | splib06a r 15784 | g.s.= |