| d (Å) | I (%) | FWHM |
|---|---|---|
| 3.86 | 12 | 0.30 |
| 3.035 | 100 | 0.28 |
| 2.845 | 3 | 0.28 |
| 2.495 | 15 | 0.28 |
| 2.284 | 29 | 0.43 |
| 2.095 | 18 | 0.27 |
| 1.927 | 5 | 0.29 |
| 1.913 | 17 | 0.28 |
| 1.875 | 17 | 0.28 |
| 1.626 | 4 | 0.29 |
| 1.604 | 8 | 0.28 |
| 1.587 | 2 | 0.29 |
| 1.525 | 5 | 0.28 |
| 1.518 | 4 | 0.30 |
| 1.510 | 4 | 0.42 |
The intensity of the peak at 2.284 Å is 29 % but on the calcite 5-586 data card the intensity is only 18 and the FWHM is large. Therefore, a peak from another phase also present.
2. The remaining peaks were listed and the peak with the largest intensity,
which was 3.34 Å, was decided to be the most appropriate
peak to search through the Hanawalt search manual from page 13 to 16 first. This
was because the first peak in the line in the Hanawalt manual is the most
intense. If there was a match then the other peaks were matched with other peaks
in the sample.
The matching peaks are shown in the table below:
| Hanawalt manual: | 3.34 | 4.26 | 1.82 | 1.54 | 2.46 | 2.28 | 1.38 | 2.13 |
| sample: | 3.343 | 4.27 | 1.817 | 1.541 | 2.458 | 2.284 | - | 2.128 |
The file no. for this phase is 5-490 and the formula is
SiO2.
This result also agrees with the electron microprobe
analysis because it indicated that Si was present.
3. The peaks for SiO2 were also eliminated from the list and the
remaining peaks listed to find the third phase. Again the most intense peak was
chosen, 2.742 Å, and was searched for in pages 30-33 of the
Hanawalt manual. If a match was found then it was seen if there was match with
the other peaks.
The matching peaks are shown in the table below:
| Hanawalt manual: | 2.74 | 2.10 | 1.7 | 2.50 | 1.94 | 1.35 | 1.34 | 0.91 |
| sample: | 2.742 | 2.102 | 1.7 | 2.503 | 1.939 | - | - | - |
The file no. for this phase is 8-479 and the formula is
MgCO3.
This result also agrees with the electron microprobe
analysis because it indicated that Mg was present.
4. The results were checked by obtaining their full PDF patterns. Both matched the two phases in the sample and the table below accounts for all the peaks in the sample:
| d (Å) | I (%) | FWHM | Phase |
|---|---|---|---|
| 4.27 | 28 | 0.27 | SiO2 |
| 3.86 | 12 | 0.3 | CaCO3 |
| 3.343 | 82 | 0.25 | SiO2 |
| 3.035 | 100 | 0.28 | CaCO3 |
| 2.845 | 3 | 0.28 | CaCO3 |
| 2.742 | 12 | 0.35 | MgCO3 |
| 2.503 | 2 | 0.36 | MgCO3 |
| 2.495 | 15 | 0.28 | CaCO3 |
| 2.458 | 10 | 0.22 | SiO2 |
| 2.284 | 29 | 0.43 | CaCO3 & SiO2 |
| 2.237 | 4 | 0.23 | SiO2 |
| 2.128 | 8 | 0.23 | SiO2 |
| 2.102 | 6 | 0.35 | MgCO3 |
| 2.095 | 18 | 0.27 | CaCO3 |
| 1.980 | 4 | 0.23 | SiO2 |
| 1.939 | 2 | 0.37 | MgCO3 |
| 1.927 | 5 | 0.29 | CaCO3 |
| 1.913 | 17 | 0.28 | CaCO3 |
| 1.875 | 17 | 0.28 | CaCO3 |
| 1.817 | 15 | 0.22 | SiO2 |
| 1.700 | 5 | 0.35 | MgCO3 |
| 1.672 | 6 | 0.23 | SiO2 |
| 1.659 | 2 | 0.24 | SiO2 |
| 1.626 | 4 | 0.29 | CaCO3 |
| 1.604 | 8 | 0.28 | CaCO3 |
| 1.587 | 2 | 0.29 | CaCO3 |
| 1.541 | 12 | 0.23 | SiO2 |
| 1.525 | 5 | 0.28 | CaCO3 |
| 1.518 | 4 | 0.30 | CaCO3 |
| 1.510 | 4 | 0.42 | CaCO3 |
The phases present in the sample are calcite (5-586), silica (5-490) and magnesium carbonate (8-479).
The search of the two unknown phases was also assisted by the microprobe analysis results because the heavier elements present were known. The overlapping of peaks of the different phases was not major making the search easier. It is assumed that the measuremnt of the sample was taken accurately as possible and preferred orientation was minimised. The close agreement of the measured intensities with the peak intensities from the actual data cards indicates that the diffraction pattern had been taken carefully.