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: Vermiculite GDS920 expanded DESCRIPT

DOCUMENTATION_FORMAT: Man_Made

SAMPLE_ID: GDS920

MATERIAL_TYPE: Expanded Phyllosilicates

MATERIAL: Expanded Vermiculite Ore

FORMULA: (Mg,Fe2+,Al)3(Si,Al)4O10(OH)2.4H2O

FORMULA_HTML: (Mg,Fe²⁺,Al)₃(Si,Al)₄O₁₀(OH)₂^.4H₂O

COLLECTION_LOCALITY: This sample is from the attic of a home in Libby, Montana supplied by the U.S. EPA in 2005.

ORIGINAL_DONOR: U.S. EPA

CURRENT_SAMPLE_LOCATION: USGS Denver, CO

ULTIMATE_SAMPLE_LOCATION: USGS Denver, CO

SAMPLE_DESCRIPTION:

The sample has a mottled golden color with minor numbers of dark grains and grains range in size from 0.5 -9 mm (Fig. GDS920.photo.1).

A modified Cincinnati floation method was carried out on this sample. The sink fraction consists of mica flakes and small elongate amphibole bundles, the later of which were mounted on a stub for SEM examination. The abundance of elongate amphibole bundles in the sink fraction indicates up to a few weight percent amphibole particles in this sample.

The sample has a spectral signature similar to that of expanded vermiculite ore from Libby, Montana, USA.

Original spectrum published in:

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

No XRD analysis is available for this sample.

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

The sample was examined with probe microanalysis. Spot analyses plot in the Libby field on the Al/Ti versus Al/[Mg/(Mg+Fe)] diagram (Fig. GDS920.microprobe.1).

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

The sample was examined with SEM and Energy dispersive spectroscopy. Elongate amphibole bundles were placed on stubs, coated with carbon, and examined under high magnification. Points analyzed with EDS are shown in color on SEM micrographs that accompany the EDS spectra. Bundles consist of individual elongate mineral particles (Figs. GDS920.SEM.1 and 2) and EDS-derived compositions are consistent with Libby amphibole (Figs. GDS920.EDS.1 and 2).

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

The spectrum is typical for a sample with predominately vermiculite and hydrobiotite with a trace biotite. The 1.40/1.42 micron band depth ratio indicates the presence of amphibole, talc, or serpentine probably at the few weight percent level. The shapes of grains of these contaminants cannot be discerned by spectroscopy. The spectral parameters plot in the Libby, MT fields (Figs. GDS920.spectrum.2 to 4).

SPECTRAL_PURITY: 1b2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns