Oxidation zones and mine wastes are metal-rich, near-surface environments, natural and man-made critical zones of ore deposits, respectively. They contain a number of minerals which, despite their metastability, occur consistently and in abundance. Field studies, presented as examples in this work, show that metastable minerals form not only directly from aqueous solutions, but also from more complex precursors, such as nanoparticles, gels, X-ray amorphous solids, or clusters. Initial precipitation of metastable phases and their conversion to stable phases is described by the Ostwald's step rule. Thermodynamic data show that there is a tendency, but no rule, that structurally more complex phases are also thermodynamically more stable. The Ostwald's step rule could then state that the initial metastable phases are structurally simple and easily assembled from aqueous solutions, nanoparticles, gels, disordered solids, or clusters. The structural similarity of the precursor and the forming phase is a kinetic factor favouring the crystallisation of the new phase. Calculation of saturation indices for mine drainage solutions show that they are mostly supersaturated with respect to the stable phases and the aqueous concentrations are sufficient to precipitate metastable minerals. In our fieldwork, we often encounter gelatinous substances with copper, manganese or tungsten that slowly convert to metastable oxysalt minerals. Another possibility is the crystallisation of various metastable minerals from solid, homogeneous ‘resins’ that are X-ray amorphous. Minerals typical for near-surface environments may be stabilised by their surface energy at high specific surface areas. For example, ferrihydrite is often described as a metastable phase but can be shown to be stable with respect to nanosised hematite.

氧化区和矿山废料分别是富含金属的近地表环境，自然和人为的矿床关键区。它们包含许多矿物质，尽管它们具有亚稳性，但它们始终如一且大量存在。作为这项工作中的例子提出的实地研究表明，亚稳态矿物不仅直接从水溶液中形成，而且还可以从更复杂的前体形成，例如纳米粒子，凝胶，X射线无定形固体或簇。Ostwald的阶跃法则描述了亚稳相的初始沉淀及其向稳定相的转化。热力学数据表明存在一种趋势，但没有规律，即结构更复杂的相在热力学上也更稳定。奥斯特瓦尔德 然后，该步骤规则可以说明，初始的亚稳相在结构上很简单，并且容易从水溶液，纳米颗粒，凝胶，无序固体或团簇中组装。前体与形成相的结构相似性是有利于新相结晶的动力学因素。矿山排水解决方案饱和指数的计算表明，相对于稳定相，它们大部分处于过饱和状态，含水浓度足以沉淀亚稳矿物。在我们的野外工作中，我们经常遇到带有铜，锰或钨的凝胶状物质，这些物质会慢慢转化为亚稳态的含氧盐矿物。另一种可能性是从固态，均质的“树脂”（它们是X射线无定形的）结晶出各种亚稳矿物。近地表环境中典型的矿物可以通过其在高比表面积处的表面能来稳定。例如，水铁矿通常被描述为亚稳定相，但相对于纳米级赤铁矿可以证明是稳定的。