Experiment #1

Summary

This experiment was to use basic, high definition x-ray fluorescence such as the HD Prime, to assign a composition to three minerals. In the experiment Copper, Limestone and Galena were analyzed.  Copper was the first model used because it would mostly contain copper (Cu) in it, making it easy to read for the first sample. Limestone, also known as calcium carbonate, was then used because it was an intermediate compound that would be slightly harder to read. Lastly, galena was chosen as a complex ore to read and understand its composition (I mainly chose it because I did not know any elements that go into its composition).

This experiment was simply a trial run to get me comfortable with the equipment and reading the graphs. Note: The graphs work by showing me spikes in counts of atoms (found on the y-axis). The x-axis tells me how much energy was being released by the x-ray (units: KeV). Based on where the peaks are found on the x-axis only certain elements will emit energy at those quantities and be counted. For example copper releases energy back when hit with energies of approximately 8.04 KeV and 8.904 KeV. The machine then reads these “coordinates” and identifies the element along with its count.

I could have very easily just read the results the machine gave me on counts of atoms found, but that would not be any fun nor would it teach me how the machine works. By using the graphs I am that much closer to understanding and appreciating how x-ray analysis works.

Figure 1. Minerals: copper, limestone, and galena.

Copper

If we look at the graph below we will see peaks in energy at around 8 KeV and 9 KeV on the x-axis. I then used an energy chart and say that copper releases a K-alpha at and 8.04 K-beta at 8.904 Looking back down at the graph we see that our peaks occur very close to those numbers, thus identifying those energy peaks at copper. This was a very simple model used to have a basic understanding of how to read the graph. (Note: K-alpha and K-beta are the emission lines of when atoms transfer to lower shells. Also, the ratio of K-alpha lines to K-beta lines is 10:1)

Figure 2. Graph from copper sample.

Limestone

The limestone sample was a little harder to read seeing as it had multiple peaks that belong to a mixture of elements. If we look at the first two peaks we see a K-alpha at approximately x=3.5 and a K-beta at approximately x=4. Then looking at the energy chart I see it matches that of calcium where K-alpha=3.691 and K-beta=4.012. Doing the same thing for the next peak I see my K-alpha is approximately 6.3, which matches iron where K-alpha=6.403. Again, I find peaks at x=14.2 and x=15.8, which closely resemble strontium where K-alpha=14.164 and K-beta=15.834.

What is interesting though is the last two peaks that closely resemble molybdenum that has a K-alpha=17.478 and K-beta=19.06. What makes this interesting is that in the list of elements that one in particular does not appear. So then what could it be? Towards the end we see a wide peak that represents the whole substance being read. Could it be then that the two peaks prior belong to nothing in particular as well?

Figure 3. Graph from limestone sample.

Galena

To say the least, galena confused me. After reviewing a full summary of data the three most common elements were lead, bismuth, and sulfur. However, when referring to the graph I cannot find half of those elements. The first small peak occurs roughly at x=2.4, making it the K-alpha for sulfur.

The next part is what makes everything confusing. After reading the manual, only k emissions should be released. Lead and bismuth however, do not release k emissions until over 70 keV, much higher than the graph goes and the machine outputs for an energy level. Now I am curious as to how the machine finds elements past 30keV when I believe that is the largest amount of energy it releases.

The remaining peaks might belong to As, Kr, and Y, but I do not want to finalize that until I learn what I am doing wrong.

Figure 4. Graph from galena sample.

Conclusions

After my first week of research I can identify easy-intermediate samples by using a graph. I still have much to learn on graphs of x-ray fluorescence, but I have made vast improvements sense the first day. This experiment has taught me the basics of how to read x-ray fluorescence graphs, compare them to the tables count (note I did not post the tables because they are very long), and learn interesting things about minerals.

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May 27th
Update

Below are updates on the graphs for Galena and Limestone. I realized for Galena, the lines I had trouble with belonged to Pb, but it was the L-orbital releasing energy rather than the K-orbital. As for limestone, I am still not sure why my last spike belongs to. Looking at the graph it would most likely be Mo, however Mo is not sound in the list of elements. Limestone may forever be a mystery to me, unless anyone has ideas.