Expanded vermiculite ores examined in this study

 Expanded vermiculite ores examined in this study: their sources and amphibole, talc, and/or serpentine impurities.

Detailed Description

Table 1.  Expanded vermiculite ores examined in this study: their sources and amphibole, talc, and/or serpentine impurities.

Notes: XRD = X-ray diffraction analysis of bulk ore samples (B) and sink fractions (S).  SEM-EDS = Scanning Electron Microscope – Energy-Dispersive X-Ray Spectroscopy.  Band Depth Ratio = 1.40/1.42-µm band depth ratio.  The use of "sodic-calcic" refers to amphiboles with compositions including primarily those of winchite, rictherite, and tremolite.  The exact amphibole species could not be determined with qualitative SEM-EDS analysis (Meeker et al. 2003; Lowers and Meeker 2004).  In this study, we use the term “elongate amphibole particle” (NIOSH 2011) to encompass all amphibole crystals longer than 5 µm with an aspect ratio greater than 3:1 whose habits are asbestiform or nonasbestiform or may have formed as a result of cleaving.  Unknown source = distinctly different spectral signature than any of those of the four major historical sources of expanded vermiculite ore.  Mixture = combination of ores, one of which is from one of four major historical sources of commercial expanded vermiculite ore.  Enoree = Enoree, South Carolina; Libby = Libby, Montana; Louisa = Louisa, Virginia; Palabora = Palabora Mine in South Africa.  Chem. = chemical; comp. = composition.  

a Sample collection location is given; otherwise city of purchase i or product manufacture k is provided when available.  

b MCM = Modified Cincinnati Method (see text for description).  Yes = detection of macroscopically visible elongate amphibole, talc, or serpentine.

c Details of MCM, microprobe, spectroscopy, XRD, and SEM-EDS analyses for expanded vermiculite ore samples can be found in the individual sample descriptions in Swayze et al. (2018).  

d Macroscopic elongate amphibole bundles were removed from the sink fraction prior to XRD analysis but were verified as amphibole by SEM analysis, thus they are listed here as being “detectable” by XRD.

e Insufficient sample volume to generate a sink fraction for analysis with XRD or MCM.

f If hours of searching revealed no amphibole, talc, and/or serpentine particles on an SEM mount then the sample was not considered to contain them.  

g XRD analysis not performed on the bulk sample and/or its sink fraction sample as noted.

h Samples, among others (Lowers and Meeker 2004), used to establish provenance fields on electron probe microanalysis diagrams (Fig. 4).  

i See a above.  

j Large Palabora flakes spatially dominate probe mounts so analyses may not have sampled smaller flakes from a non-Palabora source in this mixture of ores.  

k See a above. 


Image Dimensions: 1241 x 1446

Date Taken:

Location Taken: US