Walkerite, a new borate mineral species in an evaporitic sequence from Sussex, New Brunswick, Canada

Walkerite occurs in the Upper Halite member of the Windsor group evaporites from the Potash Corporation mine at Penobsquis, near Sussex, Kings County, New Brunswick. It is associated with halite, hydroboracite, hilgardite, volkovskite, boracite, szaibelyite and anhydrite. The crystal are colourless to white, fibrous to acicular, with H. 3, D 2.07 g/cm (super 3) ; alpha 1.516, beta 1.532, gamma 1.554, 2V (sub gamma ) 82 degrees , with alpha = a, beta = b, gamma = c. EPMA, ICP-MS and IR spectrometry gave Li (sub 2) O 0.12, Na (sub 2) O 0.13, K (sub 2) O 0.07, CaO 23.05, FeO 0.32, MgO 0.58, Cl 4.91, B (sub 2) O (sub 3) 47.17, H (sub 2) O 25.48, less O = Cl 1.11- = 100.72, leading to the idealized formula Ca (sub 16) (Mg,Li,[]) (sub 2) [B (sub 13) O (sub 17) (OH) (sub 12) ] (sub 4) Cl (sub 6) . 28H (sub 2) O. Indexed XRD powder data are tabulated; strongest lines 12.820(100), 7.785(80), 6.319(40), 5.649(30), 3.176(30), 2.570(30) Aa; a 15.52, b 22.74, c 8.761 Aa, V 3091 Aa (super 3) ; space group Pba2, Z = 1. The structure has been refined to R 0.040, the highly corrugated sheets of borate polyhedra are cross-linked by Cu and Mg polyhedra, and the Cl atoms and H (sub 2) O groups are located within the ovoid channels. The name is in honour of T.L. Walker (1867-1942) for his work on mineralogy and on the borates from Nova Scotia.