2.2. Fractions 63–125 mm and 125–250 mm
Fractions 63–125 and 125–250 mm were pre-
pared for image analysis using a microscope with
polarization optics and UV light. Thin sections
were produced in the following steps. An epoxy
plastic was carefully mixed with fluorescence
powder; it is essential that the fluorescence be
evenly mixed with the plastic. The plastic and the
fluorescence mixture was then mixed with a hard-
ener in proportion 4:1 (by weight). The mineral
powder was then added and mixed with the epoxy
in proportion 1:10 (by weight), slightly more mineral grains for the coarser fraction. The mixture
was placed in small jars, 2.5×5 cm and rotated
during hardening to prevent sedimentation. A slice
about 5 mm thick was sawed lengthways from the
centre of the jar from which a thin section was made. Due to the careful mixing and the small
proportion of particles, the mineral grains were
separated from each other, surrounded by epoxy.
The fluorescence ensures that there is a high contrast between the mineral particles and the epoxy.