A New Mineral Calcioveatchite, SrCaB11O16(OH)5·H2O, and the Veatchite–Calcioveatchite Isomorphous Series

IF 2.2 4区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Minerals Pub Date : 2024-09-02 DOI:10.3390/min14090901

Igor V. Pekov, Natalia V. Zubkova, Vladimir N. Apollonov, Vasiliy O. Yapaskupt, Sergey N. Britvin, Dmitry Yu. Pushcharovsky

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Abstract

The new mineral calcioveatchite, ideally SrCaB11O16(OH)5·H2O, is a Ca-Sr-ordered analogue of veatchite. It was found at the Nepskoe potassium salt deposit, Irkutsk Oblast, Siberia, Russia in halite-sylvite and sylvite-carnallite rocks, with boracite, hilgardite, kurgantaite, hydroboracite, volkovskite, veatchite, anhydrite, magnesite, and quartz. Calcioveatchite forms prismatic or tabular crystals up to 1 × 1.5 × 3 mm3 and crystal clusters up to 3 mm across. It is transparent and colourless with vitreous lustre. Calcioveatchite is brittle, cleavage is perfect on {010}, the Mohs’ hardness is ca 2, Dmeas is 2.58(1), and Dcalc is 2.567 g cm−3. Calcioveatchite is optically biaxial (+), α = 1.543(2), β = 1.550(5), γ = 1.626(2), 2Vmeas = 30(10)°, and 2Vcalc = 35°. The average chemical composition (wt.%, electron microprobe, H2O calculated by stoichiometry) is: CaO 7.05, SrO 20.70, B2O3 61.96, H2O 10.22, and total 99.93. The empirical formula, calculated based on 22 O apfu = O16(OH)5(H2O) pfu, is Sr1.23Ca0.78B10.99O16(OH)5·H2O. Calcioveatchite is monoclinic, space group P21, a = 6.7030(3), b = 20.6438(9), c = 6.6056(3) Å, β = 119.153(7)°, V = 798.26(8) Å3, and Z = 2. Polytype: 1M. The strongest reflections of the powder XRD pattern [d,Å(I,%)(hkl)] are: 10.35(100)(020), 5.633(12)(110), 5.092(10)(120), 3.447(14)(060), 3.362(13)(101, 051), 3.309(38)(–102), 2.862(10)(012), and 2.585(19)(080). The crystal structure was solved based on single-crystal XRD data, R1 = 0.0420. Calcioveatchite (calcioveatchite-1M) is an isostructural analogue of veatchite-1M with the 11-fold cation polyhedron occupied mainly by Sr [Sr0.902(8)Ca0.098(8)] whereas the 10-fold polyhedron is Ca dominant [Ca0.686(7)Sr0.314(7)]. The chemical composition of veatchite from five localities in Russia (Nepskoe), Kazakhstan (Shoktybay and Chelkar in the North Caspian Region), and the USA (Tick Canyon and Billie Mine in California) was studied, and it is shown to exist in nature as a continuous, almost complete isomorphous series which extends from Ca-free veatchite, Sr2B11O16(OH)5·H2O, to calcioveatchite with the composition Sr1.14Ca0.87B10.99O16(OH)5·H2O.

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一种新矿物钙钛矿、SrCaB11O16(OH)5-H2O 和 Veatchite-Calcioveatchite 同构系列

新矿物钙钛矿（理想状态下为 SrCaB11O16(OH)5-H2O）是一种钙-锶有序的钒钛矿类似物。它是在俄罗斯西伯利亚伊尔库茨克州的 Nepskoe 钾盐矿床发现的，矿床位于光卤石-钠长石和钠长石-钙长石岩石中，并与硼酸盐岩、蛭石、库尔干沸石、氢硼酸盐岩、volkovskite、钒钛铁矿、无水石膏、菱镁矿和石英一起存在。钙钒铁矿形成棱柱形或片状晶体，大小可达 1 × 1.5 × 3 立方毫米，晶体簇直径可达 3 毫米。它透明无色，具有玻璃光泽。钙橄榄石较脆，{010}上的裂隙完美，莫氏硬度约为 2，Dmeas 为 2.58(1)，Dcalc 为 2.567 g cm-3。钙钛矿具有光学双轴性 (+)，α = 1.543(2)，β = 1.550(5)，γ = 1.626(2)，2Vmeas = 30(10)°，2Vcalc = 35°。平均化学成分（重量百分比，电子显微探针，按化学计量学计算的 H2O）为CaO 7.05，SrO 20.70，B2O3 61.96，H2O 10.22，总计 99.93。根据 22 O apfu = O16(OH)5(H2O) pfu 计算得出的经验公式为：Sr1.23Ca0.78B10.99O16(OH)5-H2O。钙钛矿为单斜晶系，空间群为 P21，a = 6.7030(3)，b = 20.6438(9)，c = 6.6056(3)埃，β = 119.153(7)°，V = 798.26(8)埃3，Z = 2。聚类：1M.粉末 X 射线衍射图[d,Å(I,%)(hkl)]的最强反射是10.35(100)(020)、5.633(12)(110)、5.092(10)(120)、3.447(14)(060)、3.362(13)(101, 051)、3.309(38)(-102)、2.862(10)(012) 和 2.585(19)(080)。晶体结构是根据单晶 XRD 数据 R1 = 0.0420 解得的。钙钒钛铁矿（calcioveatchite-1M）是钒钛铁矿-1M 的等结构类似物，其 11 倍阳离子多面体主要由锶占据[Sr0.902(8)Ca0.098(8)]，而 10 倍阳离子多面体则以钙为主[Ca0.686(7)Sr0.314(7)]。研究了来自俄罗斯（Nepskoe）、哈萨克斯坦（北里海地区的 Shoktybay 和 Chelkar）和美国（加利福尼亚州的 Tick Canyon 和 Billie 矿）五个地方的钒钛铁矿的化学成分，结果表明其在自然界中以连续、几乎完整的同构系列存在，从无钙钒钛铁矿（Sr2B11O16(OH)5-H2O）延伸到钙钒钛铁矿（Sr1.14Ca0.87B10.99O16(OH)5·H2O.

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来源期刊

Minerals MINERALOGY-MINING & MINERAL PROCESSING

CiteScore

4.10

自引率

20.00%

发文量

1351

审稿时长

19.04 days

期刊介绍： Minerals (ISSN 2075-163X) is an international open access journal that covers the broad field of mineralogy, economic mineral resources, mineral exploration, innovative mining techniques and advances in mineral processing. It publishes reviews, regular research papers and short notes. Our aim is to encourage scientists to publish their experimental and theoretical results in as much detail as possible. There is no restriction on the length of the papers. The full experimental details must be provided so that the results can be reproduced.