The mechanism of [6]Li incorporation in amphiboles

The crystal structures of five monoclinic alkali amphiboles from Kajlidongri, Madhya Pradesh, India, have been refined to R indices of <2% using ~1100 observed (5?) reflections measured with MoK? X-radiation. Both site scattering refinement and an ion microprobe analysis show major Li in these crystals which fall in the series ferri-eckermannite-leakeite. These amphiboles are indicative of strongly oxidizing conditions. Li is completely ordered at the M3 site, and the compensating trivalent cations are ordered primarily at M2. Significant C-group Li has only been found in alkali amphiboles, where it seems to be locally associated with Na at the A site and Si at all neighboring T sites. -from Authors