Five celestine crystals were sampled from the (palaeo)surface intervening between the late Miocene to Pleistocene basaltic sequences of the Jabal Eghei (Nuqay) volcanic province in southern Libya and then characterised by applying a combination of the SEM–WDS, ICP/OES, PXRD and IR methods. Colour variations and related minerogenetic frameworks were also investigated. Three samples have greenish-blue-to-blue colour (480.4–482.5 nm), whereas the other two samples have blue–green colour (cyan; 489.1–494.1 nm). The colour purity ranges from 1.36–7.16. Their composition is similar, end-member celestine, in which only 1.6–4.1 at.% of Sr2+ content was substituted by Pb2+ (0.7–0.9 at.%), Ba2+ (0.5–0.7 at.%) and Ca2+ (0.2–0.8 at.%). Three samples contained vacancies, from 1.0 to 1.9 at.%. The content of other chemical elements is minor. The resulting unit-cell parameters have the ranges: a0 = 8.3578(9)–8.3705(6) Å; b0 = 5.3510(5)–5.3568(4) Å; c0 = 6.8683(7)–6.8767(2) Å and V0 = 307.17(5)–308.34(4) Å3. The PXRD and IR results are mainly in accordance with the SEM–WDS results, with a high level of correlation. However, a few discrepancies were found, producing several possible interpretations, the primary cause being a slight unit-cell axial anisotropy i.e. thermal expansion. As a consequence these results yield a new geothermometric tool that is based on the unit-cell axial anisotropy. The celestines investigated were formed during a Miocene intraplate volcanism with basaltic magmas, and associated brines lifted by the structural conduits (normal faults crosscutting the Sirt basin). The Sr-bearing fluids then poured into and over the faulted and fractured lagoon-type gypsum, anhydrite Eocene sediments. The celestine mineralisation formed within a ~368–430 K (~95–157°C) temperature range. The celestine formed at slightly elevated temperature and pressure conditions, close to the shallow subsurface environment (over 250 bars).

从利比亚南部 Jabal Eghei (Nuqay) 火山省晚中新世到更新世玄武岩层序之间的（古）表面采集了五块天青石晶体，然后结合使用 SEM-WDS、ICP/OES、PXRD 进行表征和红外方法。还研究了颜色变化和相关的成矿框架。三个样品具有绿蓝色到蓝色（480.4–482.5 nm），而其他两个样品具有蓝绿色（青色；489.1–494.1 nm）。色纯度范围为 1.36–7.16。它们的成分相似，都是端元天青石，其中仅 1.6–4.1 at.% 的 Sr 2+含量被 Pb 2+ (0.7–0.9 at.%)、Ba 2+ (0.5–0.7 at.%)取代和 Ca 2+ (0.2–0.8 at.%)。三个样品含有 1.0 至 1.9 at.% 的空位。其他化学元素含量很少。所得晶胞参数的范围为：a 0 = 8.3578(9)–8.3705(6) Å；b 0 = 5.3510(5)–5.3568(4) 埃；c 0 = 6.8683(7)–6.8767(2) Å 和V 0 = 307.17(5)–308.34(4) Å 3。PXRD和IR结果与SEM-WDS结果基本一致，相关性较高。然而，发现了一些差异，产生了几种可能的解释，主要原因是轻微的晶胞轴向各向异性，即热膨胀。因此，这些结果产生了一种基于晶胞轴向各向异性的新地温测量工具。所研究的天青石是在中新世板内火山作用期间形成的，玄武岩岩浆以及由结构管道（横切锡尔特盆地的正常断层）抬升的相关盐水。然后，含锶流体倒入断层和裂隙泻湖型石膏、硬石膏始新世沉积物中和上方。天青石矿化形成于约 368–430 K（约 95–157°C）的温度范围内。天青石是在稍微升高的温度和压力条件下形成的，接近浅层地下环境（超过 250 巴）。