R.D. Knight and R. A. Klassen

To verify mineral interpretations, grains from several samples were examined directly using detailed SEM/EDS spot analyses, and compared to the results of XRD analyses of the silt and clay-sized fraction, clay-sized fraction, and binocular petrographic methods on the 2 - 0.045 mm sized fraction.

Semi-quantitative mineralogical analyses can be achieved through calculation of the area occupied by individual minerals and normalizing the value to the total area occupied by all minerals. The calculation includes the area occupied by all particles in the image, including those touching and straddling the edges of the image. To normalize mineralogy, the area occupied by all minerals is obtained by adding all mineral maps. Depending on the type of reserach outcome the agglomerates and unidentified minerals may be included or excluded from the normalized mineralogy.

Mineral abundance relates to the percentage of the area it occupies. If area percent is assumed to be directly related to volume percent (Petruk 1989a), weight percent can be calculated by multiplying volume percent by the mineral's specific gravity and normalizing the results. Where minerals of high specific gravity have low concentrations (<5 area %), conversion of area percent to weight percent does not significantly affect the portrayal of relative abundance.

Mineral maps can be enhanced by assigning each mineral image a separate color and combining them in one layer in Adobe PhotoshopTM. For black and white illustrations, patterns may be substituted for color; larger selections of patterns are accessible in Adobe Illustrator TM or Corel Draw TM. The images can be stored as individual mineral maps as depicted below or as a combined mineral map as depicted further down this page.

The illustration below is a combined mineral map of the individual mineral maps depicted previously in this page. Note that the Fe-map displays two forms. Fe as discrete grains of possibly magnetite or as rims around many of the ilmenite grains.

References

Petruk, W. 1989a
Image analysis of minerals, In: Petruck W (ed) Short Course on Image Analysis Applied to Mineral and Earth Sciences: Mineralogical Association of Canada, Ottawa, Ontario, pp 6-18.