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# Long description

Figure 10(a)

The horizontal axis is labelled '2 theta divided by degree', and the values 0, 10, 20, 30, 40 and 50 have been marked along the axis. The vertical axis is labelled 'relative intensity', and the values 0.0 up to 6.0 have been marked along the axis. A number of curves have been drawn and labelled 'surface', '30 mm', '70 mm' and '100 mm'. The curves are vertically separated from each other, and the detail varies a little, but they all rise gently up and to the right between 10 and 20 on the horizontal axis, they all then show a broad peak a little to the right of 20, then start to head down and to the right. At about 35 on the horizontal axis all the curves show a sharp narrow peak and then flatten out. Also drawn on the graph are a large number of coloured vertical linesm, and a key identifies these as corresponding to the calcite, magnetite or jarosite standards. One of the lines produced by the magnetite standard seems to be precisely aligned with the sharp narrow peak seen on all the lines at about 35 on the horizontal axis.

Figure 10(b)

The horizontal axis is labelled '2 theta divided by degree', and the values 26, 28, 30, 32, 34 and 36 have been marked along the axis. The vertical axis is labelled 'relative intensity', and the values 0.0 up to 1.5 have been marked along the axis. The curve corresponding to '100 mm' has been drawn, starting towards the upper left and going gently down and to the right. The curve goes through a number of small indistinct peaks, and levels out around 32 on the horizontal axis, and then starts to gently climb again. Above 35 on the horizontal axis the there is a sharp peak, and to the right the line goes gently down and to the right again.

The peaks corresponding to calcite, magnetite and jarosite have again been drawn on the same axes, and both the large peak at 35 and one of the small peaks at about 29.5 are seen to be aligned with the magnetite peaks. One of the other small peaks appears to be coincident with one of the calcite peaks and the other small peak coincident with one of the jarosite peaks.