Open-File Report 96-171
Particle size may strongly influence the physical and chemical properties of a substance (e.g. its rheology, surface area, cation exchange capacity, solubility, etc.), and its measurement in rocks may yield geological information about ancient environments (sediment provenance, degree of metamorphism, degree of weathering, current directions, distance to shore, etc.). Therefore mineralogists, geologists, chemists, soil scientists, and others who deal with clay-size material would like to have a convenient method for measuring particle size distributions.
Nano-size crystals generally are too fine to be measured by light microscopy. Laser scattering methods give only average particle sizes; therefore particle size can not be measured in a particular crystallographic direction. Also, the particles measured by laser techniques may be composed of several different minerals, and may be agglomerations of individual crystals. Measurement by electron and atomic force microscopy is tedious, expensive, and time consuming. It is difficult to measure more than a few hundred particles per sample by these methods. This many measurements, often taking several days of intensive effort, may yield an accurate mean size for a sample, but may be too few to determine an accurate distribution of sizes.
Measurement of size distributions by X-ray diffraction (XRD) solves these shortcomings. An X-ray scan of a sample occurs automatically, taking a few minutes to a few hours. The resulting XRD peaks average diffraction effects from billions of individual nano-size crystals. The size that is measured by XRD may be related to the size of the individual crystals of the mineral in the sample, rather than to the size of particles formed from the agglomeration of these crystals. Therefore one can determine the size of a particular mineral in a mixture of minerals, and the sizes in a particular crystallographic direction of that mineral.
First posted March 2009
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Eberl, D.D., Drits, V.A., Srodon, J., and Nüesch, R., 1996, MudMaster: A program for calculating crystalline size distributions and strain from the shapes of X-ray diffraction peaks: U.S. Geological Survey Open-File Report 96-171, 53 p.
System Requirements and Disclaimer
Structure of MudMaster
Installation of MudMaster
Other Analytical Hints
Appendix 1: Summary of Program Inputs
Appendix 2: Recommended Settings for Clay Analyses
Appendix 3: Plots of LpG2 and XRD Patterns for Clay Mineral Basal Reflections
Appendix 4: Order of Calculation and Key Equations
Appendix 5: How to Get the Latest Version of MudMaster by FTP