Crystal structure of SrMn2(Si2O7)(OH)2 H2O, a new mineral of the lawsonite type
Crystal with the composition SrMn 2 [Si 2 O 7 ](OH) 2 .H 2 O were found in a sugilite, serandite-pectolite rich sample from the Wessels Mine, Kalahari, South Africa. The crystal structure of the nex compound with space group Cmcm, a = 6.255(1), b = 9.034(2), c = 13.397(2) A, Z = 4 was determined from X-ray single-crystal data (R = 0.048). The structure is of the lawsonite type where Al is completely replaced by Mn 3+ and Ca by Sr. [Mn 3+ O 6 ] octahedra forming edge-sharing chains parallel to a exhibit a Jahn-Teller distortion with four short and two long Mn 3+ -O distances. Sr is in eight-fold coordination and H 2 O is disordered on a split position. Together with orientite, macfallite, ru…
Zum Phosphat-Harnsteinproblem (I)
In menschlichen Harnsteinen wurden bisher die Phosphat minerale Brushit (CaHPO4 · 2 H20), Hydroxylapatit (Ca10(PO4)6(OH)2), bzw. Hydroxyl- und Carbo-natapatite der allgemeinen Formel Ca10−xHx(PO43/2C03)6(OH,l/2C03)2−x · aq (1), Whitlockit ((Ca,Mg)3(PO4)2), Octocalciumphosphat (Ca8H2(PO4)6· 5 H2O), Struvit (MgNH4PO4 · 6H2O), Magnesiumammoniumphosphat-monohydrat (MgNH4PO4 · H2O), Newberyit (MgHPO4 · 3H2O), Bobierrit (Mg3(PO4)2 · 8H2O), Hannayit (Mg3(NH4)2H4(PO4)4 · 8H2O), Magnesiumphosphat-22-hydrat (Mg3(PO4)2 • 22 H2O), sowie Hopeit Zn3(PO4)2 · 4 H2O sicher nachgewiesen.