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XRF analyzer costs between $20k to $50k, clearly small scale businesses wouldn't buy that just to analyze the elemental components of clay minerals. Hence, people tend to determine & observe its (clayey minerals) behavior and properties through those alternative methods.

Wow, that is totally way too expensive for most people I guess... We could be happy that other cheaper methods exist, even if they do not get to the same level of precision I guess.

Yeah, it does primarily depend on your purpose. XRF is mostly used for academic purposes hehehe btw, speaking of academics, please check out my recent post about my simple project during my college years :)