Rhyolite is an extrusive, igneous rock of aluminosilicate composition that upon rapid cooling forms obsidian. Obsidian is amorphous and contains limited water portions (< 2 mass%); however, secondary hydration turns it either to perlite (H₂O ≈ 2–5 mass%) or pitchstone (> 5 mass%). In the current study, kinetics of hydrous rhyolite dehydration were investigated by thermogravimetry up to 1000 °C, at heating rates of 2.5, 5, 10 and 20 °C min⁻¹ and under inert atmosphere. The mass loss is approx. 7.6 mass%, occurs along wide temperature range (100–800 °C) and is solely attributed to the release of molecular water ((H₂O)_m) and hydroxyl groups (OH). Rhyolite dehydration was considered as a solid-state reaction, and the apparent activation energy (E_a) of dehydration was calculated throughout the whole conversion range (a) by applying the isoconversional Friedman and advanced Vyazovkin methods. Both methods revealed inverse sigmoid trend in E_a values versus conversion degree, possessing almost stable value of 61 ± 5 kJ mol⁻¹ for Friedman method and 59.44 kJ mol⁻¹ for Vyazovkin method on conversion range between 0.25 and 0.75, and sharp increase at higher conversion degree. The intensive change in E_a during dehydration progression is attributed to the change in releasing species (from (H₂O)_m to OH). Raman and FT-IR spectroscopy analyses of raw and partially dehydrated samples at different stages revealed that up to 300 °C mainly (H₂O)_m is diffused out of the material causing sample enrichment in OH groups. OH release, which occurs at relatively higher temperature, is accompanied by increase in apparent E_a value of dehydration. Concerning microstructure of raw rhyolite, it exhibits a network of micro-fractures which serve as water release routes. Upon heating, more and wider fractures are created. At 600 °C, fractures merging occurs creating voids, which constitute forerunners of the expansion phenomenon. Further temperature increase causes material softening allowing local plastic deformation, which under the high pressure that is exerted by the releasing water species incites the formation of large cavities and fractures, initiating expansion.

流纹岩是一种由铝硅酸盐组成的可挤压的火成岩，在快速冷却后会形成黑曜石。黑曜石是无定形的，水含量有限（<2质量％）。然而，二次水化使其变成珍珠岩（H ₂ O≈2–5质量％）或沥青石（> 5质量％）。在当前的研究中，通过热重法在高达2.5°C，^-1 °C，5°C，10°C和20°C min ^-1以及惰性气氛下，通过热重法研究了含水流纹岩脱水的动力学。质量损失约为。7.6质量％，在宽温度范围（100–800°C）内发生，并且完全归因于分子水（（H ₂ O）_m）和羟基（OH）。流纹岩脱水被认为是固态反应，并且通过应用等转化弗里德曼法和先进的维亚佐夫金法，在整个转化范围（a）内计算了表观脱水的活化能（E _a）。两种方法均显示出E _a值相对于转化度呈反S形趋势，在0.25至0.75的转化率范围内，Friedman法和Vyazovkin法几乎稳定在61±5 kJ mol ^-1和59.44 kJ mol ^-1，并且在0.25至0.75时急剧增加。更高的转化率。脱水过程中E _a的强烈变化归因于释放物质的变化（来自（H ₂ O）_m至OH）。拉曼光谱和FT-IR光谱在不同阶段对原始和部分脱水的样品的分析表明，高达300°C的主要（H ₂ O）_m从材料中扩散出来，导致样品中的OH基团富集。在较高温度下发生的OH释放伴随着表观E _a的增加脱水的价值。关于未加工流纹岩的微观结构，它具有微裂缝网络，可以作为水的释放途径。加热时，会产生越来越多的裂缝。在600°C时，裂缝合并而形成空隙，这些空隙构成了膨胀现象的先兆。进一步的温度升高会导致材料软化，从而允许局部塑性变形，在释放的水种施加的高压下，这种塑性变形会促使大空腔和裂缝的形成，从而引发膨胀。