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 GDS908 expanded DESCRIPT

DOCUMENTATION_FORMAT: Man_Made

SAMPLE_ID: GDS908

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 Mica Grow® horticultural vermiculite from Bloomfield, Ohio and 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 numerous dark grains and grain size 0.5 - 3 mm (Fig. GDS908.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:

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 center right overlapping Enoree/Louisa fields on the Al/Ti versus Al/[Mg/(Mg+Fe)] diagram (Fig. GDS908.microprobe.1). Two spot analyses plot on the rightmost Louisa field boundary.

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. Elongate amphibole particles, likely tremolite or actinolite were detected by EDS and SEM analyses (Figs. GDS908.EDS.3 to 6 and Figs. GDS908.SEM.2; Figs. GDS908.EDS.7 and 8 and GDS908.SEM.3). No talc particles were found in the sink fraction.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

This spectrum is typical for a sample with predominately vermiculite. The 1.40/1.42 micron band depth ratio plots just above the “no detectable amphibole, talc, and serpentine” line in Figures GDS908.spectrum.2 and 3. The spectral parameters plot in the Louisa field (Fig. GDS908.spectrum.2) and Louisa/Enoree field (Figs. GDS908.spectrum.3 and 4).

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