砥部陶石のLi-トスダイト

抄録

Tosudite specimens occurring as monomineralic veinlet and as a prominent constituent of pottery stone in the Rokuro deposit, Ehime Prefecture, have been examined by X-ray, chemical, thermal and infrared methods. The basal reflections are very close to an exact integral series : the mean value of d(001) is 29.41 Å in natural state, and expands to 32.10 Å by glycerol solvation after saturation with Mg. The value of d(060) is 1.489Å. Taking the exchangeable cations into consideration, a reasonable structural formula is given as follows; chlorite layer : [Al_1.99Fe³⁺_0.03 Mg_0.01Li_0.84K_0.15Na_0.01(NH₄)_0.03](OH)₆·Al_2.00(Si_2.89Al_1.11)O₁₀(OH)₂, smectite layer : [Al_0.12Mg_0.01K_0.01(NH₄)_0.01]·5.0H₂O Al_2.00(Si_3.59Al_0.41)O₁₀(OH)₂.The chlorite layer is close to an ideal cookeite composition. However, small amounts of K incorporated into the interlayer octahedral sheet seem to be essential to construct the chlorite layer. Interlayer Al in the smectite layer is presumably combined with hydroxyl (hydroxyl Al ion), which is correlated to the distinctive endothermic reactions at 350 and 410°C. The infrared OH absorption bands and the refined z-parameters of atomic planes are also discussed in regards with accommodation of K ions in the structure of Li-tosudite.