Abstract Kernite, ideally Na2B4O6(OH)2∙3H2O, is a major constituent of borate deposits and one of the most important mineral commodities of B. The chemical composition and crystal structure of kernite from the Kramer Deposit (Kern County, California) were investigated by a suite of analytical techniques (i.e., titrimetric determination of B content, gravimetric method for Na, ion selective electrode for F, high-T mass loss for H2O content, inductively coupled plasma atomic emission spectroscopy for REE and other minor elements, elemental analysis for C, N, and H contents) and single-crystal X‑ray (at 293 K) and neutron (at 20 K) diffraction. The concentrations of more than 50 elements were measured. The general experimental formula of the kernite sample used in this study is Na1.99B3.99O6(OH)2∙3.01H2O. The fraction of other elements is, overall, insignificant: excluding B, kernite from the Kramer Deposit does not act as geochemical trap of other technologically relevant elements (e.g., Li, Be, or REE). The X‑ray and neutron structure model obtained in this study confirms that the structure of kernite is built up by: two (crystallographically independent) triangular BO2OH groups and two tetrahedral BO4 groups, which share corner-bridging O atoms to form threefold rings, giving chains running along [010], and NaO4(OH)(OH2) and NaO2(OH)(OH2)3 polyhedra. Positional disorder of two H sites of H2O molecules was observed by the neutron structure refinement and corroborated by the maximum-entropy method calculation, which consistently provided a model based on a static disorder, rather than a dynamic one. The H-bonding network in the structure of kernite is complex, pervasive, and plays a primary role on its structural stability: the majority of the oxygen sites are involved in H-bonding, as donors or as acceptors. The potential utilizations of kernite, as a source of B (B2O3 ~50 wt%), are discussed, on the basis of the experimental findings of this study.

中文翻译：

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硼矿物商品钾长石的多方法研究

摘要 Kernite，理想情况下是 Na2B4O6(OH)2∙3H2O，是硼酸盐矿床的主要成分，也是 B 最重要的矿物商品之一。研究了来自 Kramer 矿床（加利福尼亚州克恩县）的 Kernite 的化学成分和晶体结构通过一套分析技术（即 B 含量的滴定测定、Na 的重量法、F 的离子选择电极、H2O 含量的高 T 质量损失、REE 和其他微量元素的电感耦合等离子体原子发射光谱、元素分析C、N 和 H 含量）和单晶 X 射线（293 K）和中子（20 K）衍射。测量了超过 50 种元素的浓度。本研究中使用的核岩样品的一般实验式为 Na1.99B3.99O6(OH)2∙3.01H2O。总体而言，其他元素的分数是 微不足道：排除 B，Kramer 矿床中的核陨石不会作为其他技术相关元素（例如，Li、Be 或 REE）的地球化学圈闭。本研究中获得的 X 射线和中子结构模型证实，核岩的结构由两个（晶体学上独立的）三角形 BO2OH 基团和两个四面体 BO4 基团构成，它们共享角桥 O 原子以形成三重环，给出沿着 [010] 延伸的链，以及 NaO4(OH)(OH2) 和 NaO2(OH)(OH2)3 多面体。通过中子结构细化观察到 H2O 分子的两个 H 位点的位置无序，并通过最大熵方法计算得到证实，该方法始终提供基于静态无序而非动态无序的模型。核岩结构中的氢键网络复杂、普遍、并对其结构稳定性起主要作用：大多数氧位点参与氢键，作为供体或受体。在本研究的实验结果的基础上，讨论了作为 B（B2O3 ~50 wt%）来源的钾长石的潜在利用。