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DOCUMENTATION_FORMAT: Man_Made
SAMPLE_ID: GDS631
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 the Sun Gro ® vermiculite expansion plant in Pine Bluff, Arkansas around 2005.
ORIGINAL_DONOR:
CURRENT_SAMPLE_LOCATION: USGS Denver, CO
ULTIMATE_SAMPLE_LOCATION: USGS Denver, CO
SAMPLE_DESCRIPTION:
The sample has a mottled golden color with a few dark grains. Grains range in size from 1 - 8 mm (Fig. GDS631.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 that resembles a mixture of ores from Palabora Mine, Phalaborwa, South Africa and either Louisa, Virginia or Enoree, South Carolina, and possibly minor amounts of ore from a foreign source similar to sample GDS836.
Original spectrum published in:
IMAGE_OF_SAMPLE:
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
Qualitative XRD analysis of the bulk sample indicates the presence of hydrobiotite, vermiculite, biotite, phlogopite, and amphibole. (Fig. GDS631.XRD.1).
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 Palabora and Louisa/Enoree fields on the Al/Ti versus Al/[Mg/(Mg+Fe)] diagram (Fig. GDS631.microprobe.1). About a third of the spot analyses plot outside of known fields with a dense cluster on the left boarder of the Libby field near the center of spot analyses for expanded vermiculite sample GDS836 (compare Fig. GDS836.microprobe.1).
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. One elongate tremolite particle was detected with EDS and SEM analyses (Figs. GDS631.EDS.44 and 45 and Fig. GDS628.SEM.10). Prismatic diopside grains were also detected (e.g., Figs. GDS631.EDS.41 to 43, and GDS631.SEM.9).
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
The spectrum is typical for a sample with predominately hydrobiotite and phlogopite/biotite. The 1.40/1.42 micron band depth ratio plots below the “no detectable amphibole, talc, and serpentine” line in Figures GDS631.spectrum.2 and 3. The reflectance spectrum of this sample does not have a detectable 2.24-micron band so there is no symbol on Fig. GDS631.spectrum.4. The spectral parameters plot in the Mixtures field (Figs. GDS631.spectrum.2 and 3) indicating the presence of limited amounts of vermiculite from some other source(s) that was sampled by the microprobe analysis.
SPECTRAL_PURITY: 1b2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns