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 GDS455 expanded DESCRIPT

DOCUMENTATION_FORMAT: Man_Made

SAMPLE_ID: GDS455

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 came from a bag of Hoffman Ž horticultural vermiculite purchased locally in Denver in 2001.

ORIGINAL_DONOR:

CURRENT_SAMPLE_LOCATION: USGS Denver, CO

ULTIMATE_SAMPLE_LOCATION: USGS Denver, CO

SAMPLE_DESCRIPTION:

The sample has a mottled golden color with numerous dark grains and grain size 0.5 - 2 mm with rare grains about 4 mm in length (Fig. GDS455.photo.1).

A modified Cincinnati floation method was carried out on this sample. The sink fraction consists of mica flakes and small particles that were mounted on a stub for SEM examination.

The sample has a spectral signature similar to that of expanded vermiculite ore from Louisa, Virginia, 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 minor clinochlore, amphibole, albite, talc, microcline, quartz and phlogopite (Fig. GDS455.XRD.2). Qualitative XRD analysis of the bulk sample indicates the presence of vermiculite, phlogopite, biotite, and talc (Fig. GDS455.XRD.3).

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 right two Enoree/Louisa fields on the Al/Ti versus Al/[Mg/(Mg+Fe)] diagram (Fig. GDS455.microprobe.1) and between these two fields.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

The sample was examined with SEM and Energy dispersive spectroscopy. Particles from the sink fraction were placed on an SEM stub, which was coated with carbon, and examined under high magnification. Points analyzed with EDS are shown in color on SEM micrographs that accompany the EDS spectra. Talc (Figs. GDS455.EDS.6 to 8 and Figs. GDS455.SEM.3) and possible serpentine (Figs. GDS455.EDS.9 to 11 and Fig. GDS455.SEM.4) particles were found. No amphibole particles were found.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

The spectrum is typical for a sample with vermiculite. The 1.40/1.42 micron band depth ratio indicates the presence of amphibole, talc, or serpentine probably at trace levels (< few weight percent). The shape of the grains of these contaminants cannot be discerned by spectroscopy. The spectral parameters plot in the Louisa field (Fig. GDS455.spectrum.2) and Louisa/Enoree field (Figs. GDS455.spectrum.3 and 4).

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