Effects of rubidium and cesium on the structural states of potash feldspars from rare-metal pegmatites

Refinement of the crystal structure of a synthetic non-stoichiometric Rb-feldspar

“…The early data suggesting that substitution of Rb for K restricts the degree of (Al,Si) ordering Brown and Altermatt (1985) from sanidine to microcline was reaf rmed by Afonina et al, (1979). Smith (1983) …”

“…The early data suggesting that substitution of Rb for K restricts the degree of (Al,Si) ordering and Altermatt (1985) from sanidine to microcline was reaf rmed by Afonina et al, (1979). Smith (1983) Henderson (1978) the (Al,Si) disordered distribution has been synthesized hydrothermally from the low albite with the (Al,Si) ordered distribution, Meanwhile, the original view has been put forward that diffusion of Rb + and nucleation in the &Si 4 O 8rich microcline leads to formation of rubicline with the (Al,Si) ordered distribution in the granitic pegmatite (Teertstra et al, 1998b).…”

Rubidian microcline from Red Cross Lake, northeastern Manitoba

“…5;Varuträsk-Adamson 1942, Tanco and Lower Tanco-Cerny and Macek 1972, Ferreira 1984. This compositional-cum-structural range was not represented in the study of Afonina et al (1979). Also, structural states variable from monoclinic orthoclase to maximum microcline (triclinicity 0.98) are known to evolve in a single pegmatite in feldspars that show nearly uniform (Rb, Cs) contents (Fig.…”

“…The recent syntheses of end-member maximum Rbmicroclines have also shown that highly ordered feldspar framework can accommodate Rb as the dominant cation. Afonina et al (1979) examined Rb-enriched K-feldspars from three pegmatite fields and concluded that Rb and Cs do retard ordering of K-feldspars but their influence can largely be overcome by other factors such as high P of crystallization or late deformation (Fig. 5).…”