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.

中文翻译：

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奈卡巨晶是否因人类活动而变质？

自 2000 年发现奈卡洞穴的巨大石膏晶体以来，科学家们一直很着迷。人类活动改变了洞穴内的小气候，让科学家们想知道环境对晶体的潜在影响。在过去的 9 年中，我们研究了大约 70 个样本。本文报告了这些晶体表面存在的杂质的详细化学结构表征及其潜在劣化模式的实验模拟。通过岩相学、光学和电子显微镜以及实验室 X 射线衍射对选定的样品进行了研究。二维掠入射 X 射线衍射、X 射线 μ 荧光和 X 射线 μ 吸收近边结构用于识别杂质及其相关相。这些杂质是在石膏晶体形成的最后阶段沉积下来的，随后随着自然的高湿度而演变。对微气候室中晶体行为的模拟在高 CO 条件下产生了 1-4% 重量分数的晶体溶解2空气和二氧化碳下的浓缩和永久雾，以及石膏相脱水2气态环境。我们的工作表明大多数表面杂质是天然来源的。对水晶最显着的人为破坏是从洞穴中抽水。