TITLE: Nepheline HS19 DESCRIPT
MINERAL: Nepheline (Nepheline group)
COLLECTION_LOCALITY: Bancroft, Ontario
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
"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.
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 et al. (1963, vol. 4)
Found: Nepheline with Na/(Na+K)= approx 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. (Computer disk containing mineralogical software has been inoperable for weeks...)
J.S.Huebner, J. Pickrell, T. Schaefer, written communication 1994
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
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 ____ 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=