Identifying the trace element chemical fingerprint of blue colored quartz stones

Author(s)

Sydney Dale

Faculty Mentor(s)

Angela Halfpenny (Geological Sciences)

Abstract

Ellensburg Blues are a locally sourced blue quartz that retail for a higher price than blue quartz samples from other localities. We hypothesize that Ellensburg Blue samples have a distinct trace element fingerprint in comparison to blue quartz samples collected from other locations, such as Holley blue agates from Oregon. To test this hypothesis, multiple samples from known locations were analyzed using the Murdock Research Laboratories portable X-ray fluorescence spectrometer (pXRF).
To gather a large enough dataset of known and unknown origin samples for analysis, this project analyzed samples from Carl Carlson’s Ellensburg Blue mine, the Kittitas Museum blue quartz collection, the CWU Geological Sciences collection, amongst others.
Initial testing began with measuring the dimensions of each individual sample and then using the pXRF to perform bulk chemical analysis of the major and trace element compositions. The data was plotted based on its chemical composition, so similarities/differences between the samples could be identified. The Ellensburg blue samples have a distinct trace element composition with a spike in zirconium corresponding with the resulting blue color.
The known locality samples were used to create ratios between various important trace elements to produce statistical relationships and develop the sourcing key for blue quartz samples. To test the key, we ran all of the samples from known locations and checked for a correlation i.e. an Ellensburg Blue was labelled as an Ellensburg Blue by the key. Our results showed that we can use the sourcing key to authenticate blue quartz samples as Ellensburg Blues.

Keywords: “Quartz”,
“Portable X-ray fluorescence Spectrometry”,
“location sourcing”

Presentation

6 thoughts on “Identifying the trace element chemical fingerprint of blue colored quartz stones”

  1. Great presentation! I am curious if you found any coordination between sample color and zirconium levels: did Ellensburg Blues with a stronger blue hue have higher levels of zirconium, or were all the samples a similar color, or did all the samples have similar levels of zirconium?

  2. Hey Kevin Thanks for the question!
    We will be looking more into this at the next stage of our research. We have been seeing a strong correlation between the level of zirconium and the blue hue. When looking closer at the zirconium part of the spectra there are four levels/groupings within the zirconium levels. The higher the levels of zirconium the darker the blue therefore, the lower amount of zirconium the lighter the blue. What is also interesting is Carl Carlson who has been loaning us a large amount of blues has given them his own scale. We have been seeing a correlation between his scale and the level of zirconium in the blue.

  3. Excellent presentation, Sydney. It’s really interesting that you have identified a possible geochemical fingerprint of the Ellensburg Blues. I’m curious to hear whether there are other blue agates that exhibit a similar zirconium peak. I guess that will have to wait for future research!

  4. Hi Sydney, great job on the presentation! And good job so clearly finding what you were looking for with the sample!

    Here’s a question for you: are there other minerals which can incorporate Zirconium as a trace element in them that have undergone a similar analysis? It’d be interesting if there’s impure rubies or something with a similar color change.

  5. This is a great project! I noticed that the typical Holley Blue agate you have photographed here appears to contain a lot more red hues that the Ellensburg Blue. Is this due to the higher iron content? Additionally, did you notice any correlation between the opacity of the agate and the zirconium content?

  6. So cool! Great presentation! I do have a question for you, when looking at the two blue quartz samples from different locations, you can see on their graphs where their chemical compositions were the same and were they different, (showing you the Zirconium levels of course), but what about the spike on the Ellensburg blues graph that is right next to the Zirconium spike? That smaller spike is not seen in the Holley blue, is that more of the Zirconium story?

Leave a Reply

Your email address will not be published. Required fields are marked *