This dataset contains spectral parameters for absorption features found in reflectance spectra of expanded vermiculite samples. These data are provide for 52 samples of vermiculite attic insulation, horticultural products, aggregate, and packing materials derived from mines near Enoree, South Carolina; Libby, Montana; Louisa, Virginia; Palabora, South Africa; and Jiangsu, China collected from 2000 to 2016. Also included are two tables listing the spectral parameters for reflectance spectra of four expanded vermiculite samples selected to represent each of the four main historical sources of vermiculite (e.g., Libby, Montana; Enoree, South Carolina; Louisa, Virginia; and Palabora, South Africa) taken at normal spectral resolution (11 to 12 nm full width half maxiumum) and finer resolution (6nm fwhm). A third table lists the spectral parameters of spectra convolved to 11 to 12nm fwhm from the original 6nm fwhm data. Spectral parameters such as band depth were calculated by dividing the reflectance value of each spectral channel in an absorption by the corresponding reflectance value of a continuum drawn between endpoints on the shoulders of the absorption. The minimum channel of the continuum-removed data is found between the continuum endpoints, and a parabola is statistically fit to it and the two channels nearest to this minimum. The reflectance of the parabola’s center wavelength is determined, and then subtracted from 1.00 to derive the band depth of the absorption. Columns M and N list the x and y values of the contaminant non-detect line whose position passes through those samples that contain only minor to trace levels of contaminants in their sink fractions or have no Scanning Electron Microscopic evidence of contaminants (e.g., talc, amphibole, or serpentine).