Crystal Structure of Yushkinite [(Mg 0.60 Al 0.30 V 0.10 ) Σ1.0 (OH) 2 ][V 0.875 S 2 ]: An Example of a Commensurate Combination of Brucite and Sulfide Layers

A structural model of the rare mineral yushkinite [(Mg0.60Al0.30V0.10)Σ1.0(OH)2] [V0.875S2] is studied using the data of electron microdiffraction and the X-ray powder pattern. The parameters of the elementary trigonal cell are а = 3.25 A and с = 11.40 A, with the space group $${\text{P}}\,\overline {\text{3}} m{\text{1}}$$. The structure is composed of brucite and sulfide layers alternating along the с-axis, which are commensurate in the basal plane. The layer structure determines the finely dispersed nature of yushkinite morphology and perfect cleavage along {001}. The idealized yushkinite formula is refined, and trigonal symmetry is established in contrast to the hexagonal one proposed earlier.