Saliotite, a new high pressure, low temperature metamorphic phyllosilicate mineral; ordered 1:1 cookeite/paragonite mixed layer

Saliotite occurs in Permo-Triassic metapelitic rocks of the Alpujarrides nappes in the Sierra Alhamilla, Andalusia, Spain; it is found as deformed white lamellae in schists and is intergrown with pyrophyllite, paragonite, cookeite and calcite (including relics of aragonite). It is colourless in thin section, with alpha = beta 1.58-1.59, Gamma 1.59-1.6, Gamma - alpha 0.007, 2V<F128MV>a<F255D> 30-50 degrees . EPMA and ion microprobe data gave SiO (sub 2) 40.40, Al (sub 2) O (sub 3) 45.46, FeO 0.39, MnO 0.00, MgO 0.06, CaO 0.29, Na (sub 2) O 2.59, K (sub 2) O 0.35, Li (sub 2) O 1.64, [H (sub 2) O 8.82], = 100.00, leading to the idealized formula Na (sub 0.5) Li (sub 0.5) Al (sub 3) [Si (sub 3) Al]O (sub 10) (OH) (sub 5) . Indexed XRD powder data are tabulated; strongest lines 3.396(100), 4.75(80), 23.76(60), 2.966(50), 11.89(40) Aa; a 5.158, b 8.914, c 23.83 Aa, beta 94.23 degrees , V 1093 Aa (super 3) , Z = 4; D (sub calc) 2.75 g/cm (super 3) . TEM confirms the nature of a perfectly regular 1:1 ordered interstratification of cookeite (di-trioctahedral chlorite, 14 Aa) and paragonite (dioctahedral mica, 9.5 Aa); the saliotite polytype is 1M. The deformation of saliotite in the main metamorphic foliation, its inclusion in calcite veins containing relics of aragonite and the widespread crystallization of cookeite and paragonite in the late metamorphic structures show that saliotite crystallized during the early high-P metamorphic state. The estimated P-T conditions of its stability are estimated at 280-330 degrees C and 8 kbar. The name is for Pierre Saliot of Paris, for his work on high-P rocks of the Alps.