What does the 2200 nm absorption tell us about soil minerals?

[Jason37]

I’ve hit a wall trying to interpret the spectral data from my recent soil samples. The absorption features around 2200 nm are ambiguous, and I can’t decide if they indicate a specific clay mineral or just organic matter interference. My calibration set might not be robust enough for this particular geological context.

[JustinMG]

That 2200 nm area is a minefield I swear I had the same trouble. I found organic matter can look like clay on those bands. I tried a baseline correction on the spectra and then checked a different spectral window to see if the pattern moved. It helped me question what I was seeing, but it did not give a clean answer.

[AlexanderB]

Could it be that the calibration set simply doesnt fit this local geology and the real signal is masked by that mismatch?

[Jeffrey83]

I tried removing organic interference with a straightforward numeric filter and rechecking the 2200 region. The numbers moved a bit but nothing definitive showed up and the fit was worse for some samples.

[Noah26]

I keep thinking maybe I am chasing the wrong problem the bands exist sure but the bigger issue might be how the samples were prepared or how the instrument was run for that batch either way it slowed me down and I still dont have a clear read.