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 GDS332 expanded DESCRIPT

DOCUMENTATION_FORMAT: Man_Made

SAMPLE_ID: GDS332

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 house in Lansing, Michigan.

ORIGINAL_DONOR:

CURRENT_SAMPLE_LOCATION: USGS Denver, CO

ULTIMATE_SAMPLE_LOCATION: USGS Denver, CO

SAMPLE_DESCRIPTION:

Expanded vermiculite mixed with nearly equal amounts of cellulose. The vermiculite has a mottled golden color with occasional dark grains and grains range in size from 1 - 8 mm (Fig. GDS332.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 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:

Rietveld refinement XRD analysis (limited quantities of sample and no internal standard) of the Cincinnati Method sink fraction indicates the presence of major quartz, bassanite (presumably from wallboard contamination), and minor phases listed in Fig. GDS332.XRD.3. Elongate amphibole bundles were removed from the sink fraction for SEM examination prior to XRD analyses. Qualitative XRD analysis of the bulk sample indicates it contains biotite, phlogopite, vermiculite, gypsum, hydrobiotite, and amphiboles (Fig. GDS332.XRD.5).

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. GDS332.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. GDS332.SEM.1 and 2) and EDS-derived compositions are consistent with Libby amphibole (Figs. GDS332.EDS.1 and 2).

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

The spectrum is typical for a sample with vermiculite, hydrobiotite, and a trace biotite. The 1.40/1.42 micron band depth ratio indicates the presence of amphibole, talc, or serpentine probably at relatively low levels (i.e., less than a few weight percent). The shapes of the grains of these contaminants cannot be discerned by spectroscopy. The spectral parameters plot in the Libby, MT fields (Figs. GDS332.spectrum.2 to 4). Samples were spectrally measured with cellulose uniformly mixed with vermiculite.

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