PrirodaPrirodaПрирода0032-874XAkademizdatcenter Nauka62793610.7868/S0032874X20120029ArticlesСтатьиResearch ArticleMixites and petersites: New Data on the Structure of Agardite-(Ce)Микситы и петерситы: новые данные о структуре агардита-(Се)RastsvetaevaR. KРасцветаеваР. Кrast.crys@gmail.comAksenovS. MАксёновС. Мaks.crys@gmail.comShubnikov Institute of Crystallography, RASИнститут кристаллографии имени А.В.Шубникова РАН1112202012NO12 (2020)№12 (2020)111802032024Copyright ©; 2020, Издательство «Наука»2020Издательство «Наука»https://journals.eco-vector.com/0032-874X/article/view/627936

Arsenates and phosphates are rare although challenging minerals of the mixite group. Their general formula is ACu6(TO4)3–x(TO3OH)x(OH)6·3H2O, where A = REE, Ca, Pb, Bi3+, Al; T = As5+, P5+; x = 0–1, hexagonal cell parameters a ≈ 13.5 Å, c ≈ 6 Å, V ≈ 900 Å3, and space group P63/m or P63. There are two subgroups in accordance with chemical composition in T-sites: mixite (T = As) and petersite (T = P). Agardit-(Ce) CeCu6(AsO4)3(OH)6·3H2O from Clara Mine, Schwarzwald, Germany, has been investigated. Unit-cell parameters of agaradite-(Ce) are: a = 13.598(6) Å, c = 5.954(3) Å; V = 953.5(2) Å3; space group P63/m. The structure has been specified and refined to final R = 3.87% for 786 I > 3σ(I). For the first time in the structure of minerals of mixite group hydrogen atoms have been localized and hydrogen bonding has been characterized.

К редким, но очень интересным минералам относятся арсенаты и фосфаты группы миксита с общей формулой ACu6(TO4)3–x(TO3OH)x(OH)6·3H2O (где A = REE, Ca, Pb, Bi3+, Al; T = As5+, P5+; x = 0–1), параметрами гексагональной ячейки a ≈ 13.5 Å, c ≈ 6 Å, V ≈ 900 Å3 и с пространственной группой P63/m или P63. С учетом состава в T-позициях выделяются две подгруппы: миксита (T = As) и петерсита (T = P). К первой относится и изученный нами агардит-(Се) — CeCu6(AsO4)3(OH)6·3H2O, который найден в Шварцвальде, на руднике Клара (Германия). Параметры ячейки агардита-(Се): a = 13.598(6) Å, c = 5.954(3) Å; V = 953.5(2) Å3; пространственная группа P63/m, структура уточнена до R = 3.87% с использованием 786 I > 3σ(I). В этой структуре впервые для минералов группы миксита локализованы атомы водорода и исследована система водородных связей.

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