• journal_title：The Canadian Mineralogist
• Contributor：Olga V. Yakubovich ; Werner Massa ; Olga V. Dimitrova
• Publisher：Mineralogical Association of Canada
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.50.2.559
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：50
• issue：2
• firstpage：559
• section：Articles

Crystals of a potassium-rich variant of the mineral tinsleyite were obtained by hydrothermal synthesis in the system K₂O–Al₂O₃–P₂O₅–H₂O. The new phase is monoclinic, space group P2₁/n, a 9.4352(7), b 9.5254(10), c 9.4309(7) Å, β 101.421(7)°, Z = 4. Its crystal structure was solved from single-crystal data collected at 193 K and refined to R = 0.0293, including positions of all hydrogen atoms. The crystal structure is built of units of four AlO₆ octahedra sharing edges and vertices. The octahedron units are cross-linked by PO₄ tetrahedra to form a three-dimensional framework with channels along the main crystallographic [010], [001] and [100] directions, where the large K⁺ ions and H₂O molecules are distributed. The system of O – H ... O asymmetric hydrogen bonds between H₂O molecules, hydroxyl groups and framework oxygen atoms provides additional cross-linking in the structure. We show that a change in the alkalinity of the mineral-forming system correlates with the composition of the crystallizing phase and simultaneously influences the character of hydrogen bonding. The new K-rich variety of the tinsleyite is suggested as a possible mineral species. We evaluate the crystal chemistry of the leucophosphite group of minerals and the related synthetic compounds.