X-ray diffractograms of Verrucano rock sample and clay soil sample from Ennenda/Glarus, Switzerland

XRD Analysis of two soil/mineral samples from Ennenda, Switzerland: Verrucano and Clay

Artur Braun, 4. April 2026

1. Sample Description

Two powder samples from the Ennenda region (Canton of Glarus, Switzerland) were analyzed:

- Verrucano rock (reddish, collection site near Ennenda Äugsten Hütte, 47.027687, 9.106286, crushed, mortared to powder,)

- Clay sample (collected from construction pit below Äugsten cableway, valley position, 47.030724, 9.084019)

Both samples were deposited as suspensions on Si single-crystal sample holders and dried. The resulting layers were uneven and varied in thickness.

2. Geological Context

The samples originate from the Glarus Alps, a region characterized by the Glarus Overthrust (UNESCO World Heritage Site: Sardona Tectonic Arena). In this area, Permian Verrucano rocks are thrust over significantly younger flysch and sedimentary formations.

Verrucano represents a primary crystalline source material (quartz, feldspar), while the valley clay is a secondary product formed by weathering, transport, and deposition processes.

The Linth river is a major transport system, redistributing sediments from alpine catchments (including the Clariden massif) into the valley over long timescales. The clay therefore represents a mixed sediment derived in part from weathered Verrucano material.

3. Measurement

Powder X-ray diffraction patterns were recorded using Cu Kα radiation in Bragg-Brentano geometry.

4. Observations

Dominant reflections occur at approximately 26.6° and ~31.1° 2θ. No clear Si substrate peak is observed, indicating sufficient attenuation by the sample layer.

5. Peak Correction

Peak positions were corrected by referencing the quartz (101) reflection to 26.640° 2θ.

Offsets:

- Clay: −0.308°

- Verrucano: −0.375°

6. Results

After correction:

- Verrucano: ~31.10°

- Clay: ~31.26°

The remaining difference (~0.16°) is attributed to geometric effects (sample height differences).

7. Phase Interpretation

Both samples are dominated by quartz with feldspar contributions.

The clay sample additionally shows clay minerals (illite/kaolinite) and a broadened background.

8. Discussion (Geology and Origin)

The mineralogical composition supports a genetic relationship:

- Verrucano: primary crystalline source material

- Clay: secondary product of weathering and sediment transport

The proximity of sampling locations and geomorphological conditions (slope processes, debris flows, fluvial transport) suggest that the clay partially derives from Verrucano material.

The Linth river plays a key role in sediment redistribution and mixing over geological timescales. Thus, the clay represents a sedimentary mixture, whereas Verrucano reflects the primary lithology.

9. Conclusion

The XRD data demonstrate a clear mineralogical relationship between the two samples. Differences arise from weathering degree and sedimentary processes. The geological interpretation supports derivation of the clay from Verrucano-dominated source material.

Artur Braun acknowledges receiving the clay samples from a local Ennenda resident.