(a) Fit with uniform crystallite size of the sample UT97_20 containing hematite (62.76%). Circles: observed pattern; solid thin line: calculated pattern, solid thick line: calculated pattern for hematite; lower gray line: difference curve. The other determined crystalline phases in the sample were quartz (29.73%), microcline (3.60%) and calcite (3.92%). The indicated hematite peaks show the largest misfit between the observed and theoretical widths, when a uniform size of the crystallites is assumed. (b) Fit of the sample UT97_20 containing hematite by using the rotational ellipsoid model (hematite: 62.99%; microcline: 3.97%; quartz: 28.92%; calcite: 4.13%). The corresponding peaks have a suitable shape and the difference curve is almost a straight line. Symbols as in (a).