Surface impurities on giant gypsum crystals from “la Cueva de las Espadas” (Cave of Swords), Naica, Mexico

Castillo-Sandoval, Isaí; Fuentes-Cobas, L.; Pérez-Cázares, Bernardo; Ponce, Hilda Esperanza Esparza; Fuentes-Montero, María Elena; Castillo‐Michel, Hiram; Eichert, Diane; Reyes-Cortes, Ignacio; Carreño-Márquez, Iván Jalil Antón; Nápoles-Duarte, José Manuel; Montero-Cabrera, M. E.

doi:10.1007/s00710-018-0586-7

Cited by 5 publications

(10 citation statements)

References 41 publications

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“…The following phases were determined: hematite (Fe 2 O 3 ), cuprite (Cu 2 O), sphalerite (ZnS), and galena (PbS). Besides, the crystals from the CS (Castillo-Sandoval et al ., 2018) also exhibited chalcopyrite (CuFeS 2 ) and alabandite (MnS). All these phases are known to be phases that crystallize at temperatures higher than 300 °C, and mostly above 400 °C (Takeno, 2005).…”

Section: Resultsmentioning

confidence: 99%

“…Figure 6 presents a representative case of the study of a CS crystal (Castillo-Sandoval et al ., 2018). Each “pixel” represents a spatial position on the sample.…”

Section: Resultsmentioning

confidence: 99%

“…While Pb and As peaks are subject to spectral overlap in the XRF spectrum (emission lines: Pb L α 1: 10 551 eV and As K α : 10 543 eV), and thus, the elemental cartographies can be retrieved only after a careful spectral deconvolution and peak fitting, there is no such issue for the acquisition of their XANES spectrum, even if acquired in a fluorescence mode, as the excitation energy for these two elements is significantly different: the As K-edge is characterized by an absorption edge at 11.867 keV, while the Pb L 3 -edge at 13.035 keV. In Figure 6 (left), one can observe the μ -XANES spectra of As showing an intense peak (Castillo-Sandoval et al ., 2018).…”

Section: Resultsmentioning

confidence: 99%

“…Figures from samples (a–c) are reproduced with Copyright permission from Castillo-Sandoval et al . (2018). …”

Section: Methodsmentioning

confidence: 99%

“…They were selected after visual inspection and optical microscopy: 10 originated from the CS and 20 from the CC. The characterization of CS samples has been described in Castillo-Sandoval et al (2018) and is included here in the discussion for comparison. In Table I, the abbreviations for the 20 samples from the CC are given, together with the different methods used, which are briefly described in the corresponding sections.…”

Section: A Samplesmentioning

confidence: 99%

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Are the Naica giant crystals deteriorating because of human action?

et al. 2020

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The giant gypsum crystals of Naica cave have fascinated scientists since their discovery in 2000. Human activity has changed the microclimate inside the cave, making scientists wonder about the potential environmental impact on the crystals. Over the last 9 years, we have studied approximately 70 samples. This paper reports on the detailed chemical–structural characterization of the impurities present at the surface of these crystals and the experimental simulations of their potential deterioration patterns. Selected samples were studied by petrography, optical and electronic microscopy, and laboratory X-ray diffraction. 2D grazing incidence X-ray diffraction, X-ray μ-fluorescence, and X-ray μ-absorption near-edge structure were used to identify the impurities and their associated phases. These impurities were deposited during the latest stage of the gypsum crystal formation and have afterward evolved with the natural high humidity. The simulations of the behavior of the crystals in microclimatic chambers produced crystal dissolution by 1–4% weight fraction under high CO2 concentration and permanent fog, and gypsum phase dehydration under air and CO2 gaseous environment. Our work suggests that most surface impurities are of natural origin; the most significant anthropogenic damage on the crystals is the extraction of water from the caves.

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Section: Resultsmentioning

confidence: 99%

“…Figure 6 presents a representative case of the study of a CS crystal (Castillo-Sandoval et al ., 2018). Each “pixel” represents a spatial position on the sample.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…Figures from samples (a–c) are reproduced with Copyright permission from Castillo-Sandoval et al . (2018). …”

Section: Methodsmentioning

confidence: 99%

Section: A Samplesmentioning

confidence: 99%

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