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: Pyrite HS35 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS35.3

MINERAL_TYPE: Sulfide

MINERAL: Pyrite (Pyrite group)

FORMULA: FeS2

FORMULA_HTML: FeS₂

COLLECTION_LOCALITY: Rico, Colorado

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Cattierite (CoS₂). Dimorphous with Marcasite.

"SS-19. Pyrite. Rico, Colorado (35). Pyrite, FeS₂, is the most common and widespread of sulphides. It occurs in igneous, metamorphic and sedimentary rocks, as well as in veins. In the visible, pyrite displays the reflectivity vs. particle size behavior that is peculiar to opaque minerals - ie. reflectivity decreases as particle size decreases. It is also interesting that decreased absorption in the red region of the visible results in a significant contrast in reflectivity from the red to the blue, despite the sample's overall low reflectivity. In the near-infrared, the spectral behavior of pyrite changes from that of an opaque material to that of a transparent one. This sample is contaminated with grinder steel, which is probably responsible for its low reflectivity throughout. The smallest grain size is the only one which shows a rise in reflectivity to longer wavelengths, producing what appears to be an absorption edge between 1.1 and 1.5µ. We feel, however, that this is an artifact of the contamination in this sample, and that it should display a weak ferrous ion band near 1µ like marcasite, before changing from transparent to opaque behavior."

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.

IMAGE_OF_SAMPLE:
NO PHOTO

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Not Available

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

Absence of sharp spectral features suggest no secondary Fe-minerals are present in abundance.

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2c3c4_ # HS35.3 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns