TITLE: Sphalerite HS136 DESCRIPT
COLLECTION_LOCALITY: Summit County, Colorado
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
"SS-22. Sphalerite. Summit County, Colorado (136B). Sphalerite, ZnS, is the most important ore of zinc. It is typically deposited in veins by low temperature hydrothermal solutions. Sphalerite is colorless when pure, but naturally occurring samples are usually brown or black, the darkening occurring as iron substitues for zinc. This sample is a resinous brown color, typical of sphalerites. Zinc sulphide is a well known semiconductor material and, when doped with impurity ions, is a conventional phosphor. Doping with copper produces blue and /or green luminescence centers, while manganese produces orange-yellow centers. The presence of iron in the zinc sulphide acts as a luminescence killer. The macroscopic pure zinc sulphide lattice displays negligible absorption down to about 0.35µ, where the sharp absorption edge indicates the beginning of the conduction band. This sample of sphalerite does not display the near-infrared bands typical of either ferrous or ferric ions in other samples, because the iron is not in an octahedral site. It does show a rapid fall-off in reflectivity between 0.6µ and 0.35µ. This tail to the absorption edge of pure ZnS is probably caused by defects in the periodic lattice and boundary effects, as well as to some extrinsic absorption due to the impurity iron. The fall-off in reflectivity beween 2.0 and 2.5µ is an unusual feature, which we have only noticed before in aluminum compounds. The explanation given there cannot be applied here. The valence band of zinc sulphide does not extend to such short wavelength and so we tentatively suggest that it may be due to the excitation of electrons from the valence band to some fundamental level of an impurity ion."
Sieve interval 74 - 250µm.
Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1971, Visible and near-infrared spectra of minerals and rocks: IV. Sulphides and sulphates. Modern Geology, v. 3, p. 1-14.
40 kV - 30 mA, 6.5-9.8 keV
File: sphlt136.out, -.mdi
References: JCPDS #5-566
Found: sphalerite, minor additional phase
Comments: Sphalerite is the major phase with 5.41 angstroms, consistent with pure (iron-free) ZnS. There are 5 unindexexd reflections: 4 very small peaks at 3.52, 3.48, 2.12, and 1.98 angstroms and moderately sized sharp peak at 3.05 angstroms. CaCO3 was sought optically but not found.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
LIB_SPECTRA: splib04a r 4541 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.=