Synthesis of a Rb analogue of 2M1 muscovite

In the course of a study on the incorporation of Rb in muscovite, the Rb analogue of muscovite was synthesized at 600°C and 5 kbar; Rb2CO3, gamma -Al2O3 and SiO2 (cristobalite) were used as starting materials. Wet-chemical analyses and TGA data of the run products indicate that the composition is consistent with the ideal Rb end-member. SEM photographs display well-crystallized micas as run products. The XRD powder pattern can be satisfactorily indexed on the basis of a 2M1 cell, having a 5.215 + or - 0.003, b 9.059 + or - 0.005, c 20.59 + or - 0.01 A, beta 96.540° + or - 0.003°; the most likely space group is C2/c.