Characterization of Montana Grow Product David Mogk January 16, 2014 Samples of the raw material that is used in the production of Montana Grow products were characterized using X- ray Powder Diffraction (XRD), scanning electron microscopy (SEM) and back- scattered electron (BSE) imaging, and energy dispersive specrometry (EDS) for elemental analysis. 1. XRD Results: Samples were prepared by grinding in a mortar and pestle, sieved to 60 micron grain size, and analyzed using standard XRD methods using a SCINTAG XRD instrument housed at the ICAL facility, Montana State University. The results are displayed on the accompanying XRD spectra. Key results include: Most of the sample is of volcanic glass, and therefore, does not produce a well- developed XRD spectrum. The peak to background ratios are very small, indicating that only a minor component of the material is actually crsytalline. Minerals that have been identified include: quartz (which probably occurs as a secondary phase in the glassy matrix, see SEM images), cristobalite (which is the high temperature variety of silicon dioxide that commonly occurs in volcanic rocks), and a high temperature (unordered) alkali feldspar that is part of the solid solution series between Na and K end members, anorthoclase. 2. Petrographic Analysis: A series of photomicrographs were obtained using standard thin sections on a petrographic microscope. Images were acquired at both 40X and 100X in both plane polarized light and cross- polarized light. Glass is amorphous (and isotropic), so it will appear to be black when viewed through cross polarized light. Phenocrysts (primary igneous crystals) observed in these samples include: quartz, sanidine/anorthoclase, and rare biotite. Open space vesicles are observed in many of the samples, and these are commonly rimmed by quartz that was probably deposited by crystallization from a vapor phase. 3. Scanning Electron Microscopy: Images were obtained in both scanning electron imaging and back- scattered electron imaging modes. The standard SEM images are used to show textural relations; BSE images are used to differentiate phases present as the brightness of the signal is related to the mean atomic number (in general, denser materials are brighter in BSE images). Phenocryss in these images are alkali feldspar, sanidine/anorthoclase rims vesicles and devitrified flow bands, a single biotite grain can be observed in one image. A representative EDS spectrum of the alkali feldspar is included.
Figures 1 and 2: Plane polarized light and cross polarized light, 4X, FOV 2.5 mm. Most of the matrix is volcanic glass; the phenocryst is alkali feldspar.
Figures 3 and 4: PPL and XN photomicrographs, 10X. Most of the matrix is volcanic glass; vesicles are rimmed by devitrified glass or secondary precipitate of quartz.
Figures 5 and 6: PPL and XN photomicrographs, 4X. The phenocryst is alkali feldspar (twinned), and most of the matrix is volcanic glass except for fine grained quartz.
Figure 7: XN Photomicrograph 10X; volcanic glass in the matrix, devitrified flow bands and secondary quartz. Figure 8: XN photomicrograph 10X. Sanidine/anorthoclase phenocryst in glassy matrix.
Figure 9 PPL photomicrograph of representative glassy matrix; 10X. Figure 10 XN, 10X. Matrix of volcanic glass with minor quartz.
SEM image of polished thin section; most of the material is volcanic glass and a central vesicle is rimmed by quartz. BSE image of the same area as above.
SEM image of a sanidine/anorthoclase phenocryst set in a volcanic glass matrix. BSE image of the same area as above; some secondary calcite is present; the bright round rim of one vesicle is sanidine.
BSE image of volcanic glass (darker gray), with brighter sanidine rimming the vesicles. BSE image of volcanic glass, brighter rims of sanidine around the vesicles and the bright rectangular grain at the top of the image is biotite.
BSE image of one of the devitrified bands, 1600 X. BSE image of glassy matrix, with sanidine rims in vesicles and flow bands.
BSE image of sanidine phenocryst, sanidine rimming vesicles and volcanic glass in the matrix. Representative EDS spectrum of an alkali feldspar phenocryst; Na and K solid solution is evident indicating that this mineral is anorthoclase or sanidine.