This paper articulates and fills a clear gap in the literature: the scarcity of measurements of mineral dust optical properties beyond a wavelength of ~15 um. The paper is also well written and the methodology rigorous, following previous very well-regarded work by the main authors. I do have two important comments about the framing of the paper that should be addressed before publication.

Major comments:

• The authors take two samples of Icelandic dust to be representative of high-latitude dust. However, because Iceland is a volcanic island the mineralogical composition of its dust is likely to be quite different (more basaltic and darker) than that of other high-latitude sources, which are normally more silicate and quartz rich. The mineralogy of Icelandic dust might thus be an outlier among high-latitude dust sources and should not be taken as representative of high-latitude dust sources. I recommend that the authors replace “high latitude dust” with “Icelandic dust” in the title, abstract, and so forth. If the authors do want to take the Icelandic dust as representative then they should provide evidence that this is reasonable to do, for instance from a comparison of the mineralogy of Icelandic dust to that of other high-latitude sources.
• The authors state at various locations in the manuscript that the optical properties in the far infrared region (beyond 15 um) are important to climate and remote sensing. However, conventional wisdom is that (dust) absorption (well) outside of the atmospheric window does not matter much because the atmosphere is very opaque beyond 15 um due to abundant absorption by water vapor. So I have a hard time imagining that the dust interaction with radiation would normally matter much for Earth’s radiation budget. Two exceptions worth highlighting are for dust in the upper troposphere and for dust in the Arctic (mentioned in the paper), but the dust concentration is very low in both locations. A clearer argument could be made for remote sensing, as long as it’s made clear that this would only work in the upper troposphere / stratosphere and the dry poles. If the authors do want to make the point that dust interactions with radiation beyond 15 um matter for Earth’s climate, I recommend they show (1) Earth’s outgoing radiation as a function of wavelength and (2) the height in the atmosphere at which the optical depth to TOA equals 1 (the emission height) for one or more standard profiles (e.g., mid-latitude summer). That can make at least a qualitative argument that the dust optical properties for wavelengths larger than 15 um matter for Earth’s radiation budget.

Minor comments:

• Line 68: the 88% here seems very specific. My recollection of these papers also is that the error bar on the net DRE overlapped with zero, meaning that the dust-radiation interactions in the infrared could be >100% of those in the shortwave spectrum.
• Many citations that are part of the sentence are listed with parentheses, which is a bit tedious to read. For instance, line 263 should probably be “The Sadrian et al. (2023) dataset…” instead of “The (Sadrian et al., 2023) dataset…”

The paper discusses the importance of further measurements of dust spectral properties in the mid-infrared (~3–15 μm) and, particularly, in the far-infrared (~15–100 μm) regions, as they may have a substantial effect on total dust direct radiative forcing and climate model estimations. The study uses 13 dust samples from low-, mid-, and high-latitude regions, employing dust-KBr pellets to obtain absorbance spectra. The results show that the spectral signatures of low- and mid-latitude dust are in good agreement with past studies. However, dust collected from high-latitude regions exhibits different spectral characteristics due to its distinct composition, which is primarily dominated by amorphous minerals.

This study makes a valuable contribution by adding new dust spectral data from low-, mid-, and high-latitude regions to the global library of mineral dust spectra. As more remote sensing instruments are being developed to cover the mid- and far-infrared spectra and are planned to monitor aerosol particles, studies like this can significantly help reduce uncertainties in estimating the radiative effects of dust and in quantifying their abundance through remote sensing retrievals.

Comments:

• For Figure 2: Since the absorbance spectra for the samples have already been offset, you can label the y-axis as “Absorbance (offset for clarity).” This is a more traditional approach and improves the overall clarity of the plot.
• For line 245: where it is mentioned “A third band at 14 μm is potentially associated with anorthite or augite, which are the dominant minerals by mass, but no literature spectral data for these minerals are available at these wavelengths to confirm this attribution.”

You can find the transmission spectra of pure minerals (~ 2.5-25 um), including anorthite and augite, for comparison purposes in: Salisbury, J. W., Walter, L. S., Vergo, N., & Daria, D. M. (1991). Infrared (2.1–25 μm) spectra of minerals. Johns Hopkins University Press. ISBN: 978-0801844232.

• That would be good if you could remove the white columns on both sides of Fig. 1.
• Line 275: edit LLMD. It should be LMLD.