A novel 3D sampling method of geological rock-core using X-ray fluorescence

Alexandru Enciu

REVIEW 3 major objections 4 minor 15 references

A novel 3D sampling method of geological rock-core using X-ray fluorescence

T0 review · 3 major / 4 minor · reviewed 2026-08-10 · deepseek-v4-flash

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Pith's one-line read A proof-of-concept scanner maps 1D, 2D, and 3D element distributions over an intact cylindrical rock core using X-ray fluorescence, without cutting the sample.

desk verdict A real proof-of-concept for whole-core cylindrical XRF mapping—more instrument note than quantitative geochemistry, but the idea is new and worth a referee's time. read the letter →

arxiv 2501.02366 v1 pith:OCJV6F7Y submitted 2025-01-04 physics.ins-det physics.app-phphysics.chem-ph

Alexandru Enciu This is my paper · ORCID

classification physics.ins-detphysics.app-phphysics.chem-ph PACS 07.85.-m

keywords X-rayfluorescencerock-corescanning3Delementalmappingsurfacereconstructioncylindricalscannon-destructiveanalysisbrecciastratigraphy

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper demonstrates a proof-of-concept X-ray fluorescence scanner that analyzes the curved outer surface of a geological rock core directly, instead of requiring the core to be cut in half to expose a flat surface. It claims that one automated helical scan produces the 1D stratigraphic element logs, 2D element maps, and a 3D surface reconstruction that currently require two different commercial instruments and an invasive preparation step. If the method works as described, routine core screening could become faster and cheaper, and surface element distributions and grain-scale clusters would be visible before any destructive analysis is chosen. The demonstration uses one breccia sample, and the author notes that centering the sample and supporting its weight are the main practical difficulties.

What carries the argument

The central object is the cylindrical scan trajectory: the sample rotates with angular step $\theta = 2 \arcsin(d/(2r))$ so that the surface pixel width $d$ stays square, and after each full revolution the sample moves vertically by $d$, addressing every surface point in cylindrical coordinates $(r, \varphi, h)$. The analysis chain filters the pulse-height spectra in Fourier space, calibrates the energy scale with pure-element standards, finds peaks from first and second derivatives, and applies only the detector efficiency correction $I_{\text{corrected}} = I_{\text{measured}}/\varepsilon(E)$ before unfolding the data into 1D layer sums, 2D $(\varphi, h)$ intensity maps, and a 3D mesh. This scan geometry, rather than a new physical principle, is what lets one pass replace the destructive half-core preparation step.

What would settle it

Scan a machined cylinder of uniform, known composition with the same protocol and check whether the corrected intensity of a single element stays constant over all rotation angles and heights; any systematic variation would show that geometry and matrix effects, not chemistry, are producing the map features.

Watch

Extended reading notes

Core claim

The paper reports that a tabletop arrangement of an X-ray detector, a collimated silver-target X-ray generator, and a motorized rotary-and-translation stage can scan an intact breccia core 60 mm in diameter and 80 mm tall at 0.5 mm pixels, and from the collected spectra reconstruct stratigraphic element profiles and 2D and 3D surface maps for Si, Cl, K, Ca, Ti, and Fe. According to the author, this single cylindrical-surface scan samples roughly six times more area than the standard flat half-core geometry, combines the 1D logging capability of a conventional core scanner with the 2D mapping of a flat-sample micro-XRF scanner, and requires no sample preparation. The maps are intentionally qualitative: pixel values are relative indicators of abundance, with only the detector efficiency corrected, and the claimed savings in time and cost follow from skipping the core-cutting step.

Load-bearing premise

The method assumes that a pixel's measured X-ray intensity, corrected only for detector efficiency, faithfully reflects how much of an element is present at that spot on a curved, rough surface, with no correction for how the surrounding material absorbs or boosts the signal, or for distance and angle changes while the core rotates.

Editorial extensions

If this is right

Intact cores can be screened non-destructively before any cutting, preserving the material and reducing preparation time and cost.
A single scan yields stratigraphic profiles, unwrapped cylindrical maps, and a 3D surface mesh, covering both core-logging and surface-mapping needs in one dataset.
Scanning the full cylinder rather than a flat half-core increases the analyzed surface by about a factor of six, improving counting statistics for 1D element profiles.
With 0.5 mm pixels, the 2D and 3D maps make grain sizes and mineral clusters visible and allow regions of interest to be targeted for further analysis.
The method merges the 1D core-logging function of a fan-beam core scanner with the high-resolution 2D mapping of a flat-sample micro-XRF scanner into one data-collection process.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

Because the paper applies no matrix absorption or enhancement correction and no geometric normalization, the maps are relative; turning them into true abundances would require calibration standards or a radiation-transport correction, and small intensity changes should not be read as pure chemical gradients.
A natural next step the author leaves implicit is to record the actual local radius and tilt during the scan with a laser profiler, which would correct for distance and angle variations and allow non-cylindrical or irregular cores to be scanned reliably.
The same helical XRF sampling scheme could transfer to other cylindrical objects, such as ice cores, archaeological cores, or industrial pipe surfaces, wherever non-destructive surface chemistry is wanted.
The stated sixfold area advantage assumes an ideal cylinder; for rough or off-center samples the usable area and the reliability of the 1D layer sums will depend on how well the scan geometry can be registered to the true surface.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

It's a genuine proof of concept for something I haven't seen before: a tabletop XRF scanner that maps the whole cylindrical surface of an uncut rock core, producing 1D, 2D and 3D element maps from one pass. That is the actual novelty, and it's real. The authors are upfront that the output is qualitative relative intensities, and they describe the hardware and processing chain clearly enough to reproduce the mechanics: stepper-motor axes from old printers, an Amptek Si-PIN detector, a 0.5 mm collimated Ag source, standard Fourier filtering, energy calibration with pure metals, derivative-based peak finding, Gaussian-plus-polynomial fitting, and detector efficiency correction. For an instrument proof of concept, that is honest and adequate.

The soft spots are real but not fatal. The stress-test concern is fair: with only the detector efficiency correction in Eq. 5, pixel-to-pixel intensity differences on a rough breccia could be topography or matrix effects as much as chemistry. The paper even admits centering and Y-axis positioning problems. However, the paper sells this as a screening tool, not a quantitative assay, so the missing validation is a gap rather than a flaw in the central claim. A referee should ask for a scan of a homogeneous standard or a comparison with a conventional half-core scan, plus uncertainty estimates. Also, the "6 times larger" scanned-area claim is wrong; the full cylindrical surface is π times the flat cut face, not 6. And no data or code are released, which makes independent checking harder.

My own read is close to the reader's: conditional acceptance is the right verdict. The instrument concept is plausible and the processing is standard, so the proof-of-concept claim stands. But the scientific output of the method—element maps that reflect chemistry rather than geometry—is not yet demonstrated. That limits the paper to a hardware demonstration, which is fine, but it should be labeled as such.

Who benefits? Geologists who do core logging and want a cheap, non-destructive first pass before deciding where to cut. The paper is also a useful teaching example of a homemade XRF scanner. It deserves a serious referee: the idea is new and the execution is transparent, even if the quantitative claims need trimming. I'd send it to review with a request for one validation experiment and a corrected area calculation.

Referee Report

3 major / 4 minor

Summary. The paper presents a proof-of-concept tabletop X-ray fluorescence scanner for geological rock cores. The device rotates a cylindrical core about its axis while translating it vertically, and a collimated X-ray source and Si-PIN detector acquire spectra at each point. A custom LabView analysis pipeline applies Fourier-domain filtering, linear energy calibration from pure-element standards, automatic peak finding with Gaussian peak and polynomial background fitting, and a detector-efficiency correction (Eq. 5). The output is displayed as a summed spectrum, 1D stratigraphic profiles, 2D angle-versus-height intensity maps for Si, Cl, K, Ca, Ti, and Fe, and a 3D cylindrical mesh. The authors argue that the method avoids the usual half-core cutting step and allows 1D, 2D, and 3D elemental mapping of the whole core surface.

Significance. If the reconstructed intensity variations are faithful to elemental abundance, the method offers a low-cost, non-destructive screening tool for whole drill cores, with potential to complement or partially replace destructive half-core analysis. The hardware design, scan geometry, and processing steps are described in enough detail to be reproduced, and the use of open and low-cost components (Arduino, recycled printer parts) is a practical strength. However, the central scientific claim—that the resulting maps represent elemental distribution over the rock surface—is not yet supported by any quantitative validation. The only correction applied, detector efficiency, does not account for source-sample-detector geometry, surface curvature, roughness, or matrix effects, all of which are acknowledged in the text. A homogeneous-standard validation or an independent reference measurement is needed before the maps can be interpreted geologically.

major comments (3)

[Section 3, Figs. 3–4; Eq. (5)] Eq. (5) corrects each measured peak area only for the detector energy efficiency ε(E). For a rough, curved, heterogeneous breccia surface, the detected X-ray intensity also depends on the local source–sample distances, on the incidence and take-off angles, on surface curvature, and on matrix absorption and enhancement. The paper itself acknowledges the matrix dependence of thick-sample XRF in the Introduction and reports centering and Y-axis positioning difficulties for the analyzed sample in Section 3. Without a validation measurement on a homogeneous cylindrical standard, or a direct comparison against a conventional flat-surface XRF dataset for the same core, the spatial intensity variations in the 2D maps of Fig. 4 and the stratigraphic profiles of Fig. 3 cannot be separated from topography and positioning artifacts. This validation is load-bearing for the central claim that the method reveals elemental distribution over the surface; I request that it be added and that the residual geometric uncertainty be quantified.
[Section 3 (Fig. 4), Section 4] The statement that the 2D maps allow 'measurements of the grain size of the sample, granulometry' is not supported by any defined procedure. No segmentation algorithm, threshold criterion, or error analysis is given, and the color scale is a relative corrected intensity, not a calibrated concentration or a defined quantity. Either provide a concrete, repeatable method for extracting grain-size distributions from the maps together with an uncertainty estimate, or remove the granulometry claim from the abstract and conclusions.
[Section 2, Eq. (2)] The Fourier-domain noise filter contains a free cutoff parameter ucrit, but the paper does not state the value used or test the sensitivity of the peak-area results to this choice. Since the filtered spectrum is the input to the automatic peak-fitting routine, an arbitrary cutoff could bias the reported intensities. The authors should report the chosen ucrit and show a sensitivity test, for example by varying ucrit over a reasonable range and documenting the change in the final peak areas.

minor comments (4)

[Eq. (2)] The piecewise definition of H(u) is typeset incorrectly; the expression 'H(u) = ( 1, u ≤ ucrit 0, u > ucrit G(u) = F(u)H(u)' lacks a closing brace and line break, making the equation ambiguous.
[Section 2, scanning parameters] The paper states a scan speed of 5 mm/s and a pixel size of 0.5 mm, but does not specify whether the motion is continuous or step-and-measure, nor the effective dwell time per pixel. This information is necessary to reproduce the measurement and to assess counting statistics.
[Section 2, energy calibration] The energy calibration uses standards from Ca upward, but the mapped elements include Si (Kα ≈ 1.74 keV) and Cl (Kα ≈ 2.62 keV), which lie below the lowest calibration point (Ca Kα ≈ 3.7 keV). The paper should justify the linear extrapolation to lower energies or include a low-energy standard.
[Section 4] The claim that the scanned cylindrical surface is '6 times larger than in the classical method' is arithmetically incorrect: the ratio of the full cylinder area (2πrh) to the flat rectangular half-core surface (2rh) is π, not 6. The sentence should be corrected or the comparison geometry specified.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the elemental maps are direct measurements of corrected peak areas plotted at scan coordinates, with no fitted model used to predict the same data.

full rationale

The paper reports a proof-of-concept 3D XRF scanner. Its derivation chain is: acquire spectra, filter noise (Eqs. 2-3), calibrate energy with pure-element standards (Eq. 4), find peaks and fit peak areas, apply detector efficiency correction (Eq. 5), and plot the resulting I_corrected values as 1D, 2D, and 3D maps. None of these steps fits a model to the measured map and then predicts that same map. The energy calibration constants (a, b) and the background polynomial coefficients are per-run instrumental calibrations, not parameters of the elemental distribution. The efficiency correction epsilon(E) is a detector property, not a sample-derived parameter, so I_corrected = I_measured / epsilon(E) does not reduce the map to its own input; it is a standard instrument correction. The maps are therefore direct measurements rather than predictions from a fitted model. The paper's limitations are acknowledged in Section 3 (sample centering and Y-axis positioning difficulties) and in the Introduction (qualitative information without matrix corrections), but those are correctness and validation concerns, not circularity. The references are external, and there is no self-citation chain that carries a load-bearing premise. Accordingly, no circular step is present.

Assumptions & free parameters 2 free parameters · 4 assumptions · 0 invented entities

The central claim relies on standard XRF physics, quoted in the introduction, and on several unvalidated domain assumptions: that the curved-surface scan maintains constant geometry, that detector-efficiency correction suffices for relative comparisons, and that matrix effects can be ignored. No new theoretical entity is introduced; the instrument is assembled from off-the-shelf parts. The only fitted numbers are calibration constants, not outputs tied to the final map in a self-referential way.

free parameters (2)

Fourier cutoff ucrit = not quantified
Hand-chosen high-frequency cutoff in Eq. 2; affects noise filtering and peak shapes in all reported maps.
Energy calibration coefficients a, b = not listed numerically
Fit by linear regression over Ca, Fe, Ni, Cu, Au standard spectra in Eq. 4; used for channel-to-energy mapping, not a predictive constant for the final maps.

assumptions (4)

domain assumption Characteristic X-ray peak area is monotonically related to elemental abundance in the probed volume
Invoked throughout Section 2 and Results; no matrix correction is applied, so the relation is assumed to hold for relative comparison on a rough rock surface.
domain assumption X-ray generator-sample and detector-sample distances and the 45-degree angle remain effectively constant over the curved sample surface
Used in Section 2 when defining the scan geometry; the paper acknowledges centering and Y-axis positioning issues in Section 3 but does not correct for geometric intensity variation.
domain assumption Detector efficiency correction alone is sufficient to compare relative abundances across elements and locations
Eq. 5 applies only the detector efficiency epsilon(E); matrix absorption and enhancement, and surface roughness corrections, are absent from the analysis.
standard math Energy calibration is linear across the measured range
Eq. 4 assumes E = a*x + b with a,b from a linear fit; the paper does not discuss nonlinearity or residuals.

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Cite this review

Pith. "Pith review of A novel 3D sampling method of geological rock-core using X-ray fluorescence." pith.science (2026). https://pith.science/paper/OCJV6F7Y

@misc{pith2026250102366,
  author       = {Pith},
  title        = {Pith review of: A novel 3D sampling method of geological rock-core using X-ray fluorescence},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/OCJV6F7Y}},
  note         = {Machine review of arXiv:2501.02366}
}

read the original abstract

The current work describes a proof of concept of a 3D XRF scanner, which is able to perform elemental analysis over the cylindrical surface of geological rock-core and to reconstruct a 1D, 2D and a 3D elemental map of the scanned area. The presented method will reduce the time and cost for sample preparation, but also will reveal more information about the distribution of the elements over the surface.

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

15 extracted references · 14 canonical work pages

[1]

A novel 3D sampling method of geological rock-core using X-ray fluorescence

Introduction Since 1932 X-ray fluorescence (XRF) spectroscopy was considered a quali- tative and quantitative elemental analysis by Hevesy, Coster and others who inves- tigated in detail the method [1]. XRF analysis can cover a large range of elements (Z>10) with high resolving power, being able to detect concentrations down to a few ppm [1, 2, 3]. For th...

work page Pith review arXiv 1932
[2]

Materials and Methods The proposed method consists of a 3D scan of the rock-core which allows for a 3D reconstruction of the superficial distribution of elements in the sample. This scan would serve as a preliminary map containing relative intensities of the elements and does not involve any preparation of the sample, reducing the costs and the complexity...

work page
[3]

X-Ray Generator; 3

X-Ray Detector; 2. X-Ray Generator; 3. Rotary table R; 4. Translation axis X; 5. Translation axis Y The software integration of the entire experimental set was performed using the visual programming language LabView® [9]. The software allows separate control of each component and its parameters. The scanning sequence and data aquisition (DAQ) are performe...

work page
[4]

The sum of all measured spectra is illustrated in logarithmic scale in Figure

Results and Discussion In this section will be presented the results of the tabletop XRF scanner which scans the surface of the cylindrical rock-core in a manner that allows with collected data to reconstruct 1D, 2D and 3D elemental maps. The sum of all measured spectra is illustrated in logarithmic scale in Figure

work page
[5]

This type of representation allows a better assembly view of the elements present in the sample

The elements are identified and the peaks and background are fitted. This type of representation allows a better assembly view of the elements present in the sample. 6 1 FIGURE 2. Spectra summation of all measured points Figure 3 displays the element profiles along the rock-core helping to under- stand the geochemical content of the sample in each geologi...

work page
[6]

Conclusions The proposed method offers high quality images of rock-core surface at high scanning speed with minimal sample preparation and due to the small pixel size, the quality of the images was good and allowed to establish if any ROI needs fur- thermore analysis. The current method combines the scanning capabilities of the two devices (ITRAX® and M4T...

work page
[7]

Markowicz, https://doi.org/10.1201/9780203908709

Handbook of X-Ray Spectrometry, Second Edition,Edited ByRene V an Grieken, A. Markowicz, https://doi.org/10.1201/9780203908709

work page doi:10.1201/9780203908709
[8]

Beckhoff,B

Handbook of Practical X-Ray Fluorescence Analysis,B. Beckhoff,B. Kanngießer , N. Langhoff R. Wedell, H. Wolff, https://doi.org/10.1007/978-3-540-36722-2

work page doi:10.1007/978-3-540-36722-2

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[9]

Bertin, https://doi.org/10.1007/978-1-4613-4416-2

Principles and Practice of X-Ray Spectrometric Analysis, Eugene P . Bertin, https://doi.org/10.1007/978-1-4613-4416-2

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Croudace, Ian and Rindby, Anders and ROTHWELL, R.. (2006). ITRAX: Description and Eval- uation of a New Multi-Function X-ray Core Scanner . Geological Society, London, Special Pub- lications. 267. 51-63. 10.1144/GSL.SP .2006.267.01.04. A novel 3D sampling method of geological ...

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Flude, Stephanie and Haschke, Michael and Storey, Michael. (2017). Application of benchtop micro-XRF to geological materials. Mineralogical Magazine. 81. 10.1180/min- mag.2016.080.150

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Barker , Rocky and Barker , Shaun and Wilson, Siobhan and Stock, Elizabeth. (2020). Quanti- tative Mineral Mapping of Drill Core Surfaces I: A Method for µ XRF Mineral Calculation and Mapping of Hydrothermally Altered, Fine-Grained Sedimentary Rocks from a Carlin-Type Gold Dep...

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Matsyendra Kumar Shukla, Anupam Sharma, A brief review on breccia: it’s contrasting origin and diagnostic signatures, Solid Earth Sciences, V olume 3, Issue 2, 2018, Pages 50-59, ISSN 2451-912X, https://doi.org/10.1016/j.sesci.2018.03.001

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2007 doi

Pith tools

Reviewed August 10, 2026 · model on record in the stance chip above.

[1] [1]

A novel 3D sampling method of geological rock-core using X-ray fluorescence

Introduction Since 1932 X-ray fluorescence (XRF) spectroscopy was considered a quali- tative and quantitative elemental analysis by Hevesy, Coster and others who inves- tigated in detail the method [1]. XRF analysis can cover a large range of elements (Z>10) with high resolving power, being able to detect concentrations down to a few ppm [1, 2, 3]. For th...

work page Pith review arXiv 1932

[2] [2]

Materials and Methods The proposed method consists of a 3D scan of the rock-core which allows for a 3D reconstruction of the superficial distribution of elements in the sample. This scan would serve as a preliminary map containing relative intensities of the elements and does not involve any preparation of the sample, reducing the costs and the complexity...

work page

[3] [3]

X-Ray Generator; 3

X-Ray Detector; 2. X-Ray Generator; 3. Rotary table R; 4. Translation axis X; 5. Translation axis Y The software integration of the entire experimental set was performed using the visual programming language LabView® [9]. The software allows separate control of each component and its parameters. The scanning sequence and data aquisition (DAQ) are performe...

work page

[4] [4]

The sum of all measured spectra is illustrated in logarithmic scale in Figure

Results and Discussion In this section will be presented the results of the tabletop XRF scanner which scans the surface of the cylindrical rock-core in a manner that allows with collected data to reconstruct 1D, 2D and 3D elemental maps. The sum of all measured spectra is illustrated in logarithmic scale in Figure

work page

[5] [5]

This type of representation allows a better assembly view of the elements present in the sample

The elements are identified and the peaks and background are fitted. This type of representation allows a better assembly view of the elements present in the sample. 6 1 FIGURE 2. Spectra summation of all measured points Figure 3 displays the element profiles along the rock-core helping to under- stand the geochemical content of the sample in each geologi...

work page

[6] [6]

Conclusions The proposed method offers high quality images of rock-core surface at high scanning speed with minimal sample preparation and due to the small pixel size, the quality of the images was good and allowed to establish if any ROI needs fur- thermore analysis. The current method combines the scanning capabilities of the two devices (ITRAX® and M4T...

work page

[7] [7]

Markowicz, https://doi.org/10.1201/9780203908709

Handbook of X-Ray Spectrometry, Second Edition,Edited ByRene V an Grieken, A. Markowicz, https://doi.org/10.1201/9780203908709

work page doi:10.1201/9780203908709

[8] [8]

Beckhoff,B

Handbook of Practical X-Ray Fluorescence Analysis,B. Beckhoff,B. Kanngießer , N. Langhoff R. Wedell, H. Wolff, https://doi.org/10.1007/978-3-540-36722-2

work page doi:10.1007/978-3-540-36722-2