The species status of volkonskoite (M.M. 48-297; M.A. 86M/0833) has been unclear, so two specimens from Mt Efimiatsk, the type locality, have been examined. Chemical analyses show major Cr (>20 wt.% Cr2O3) and a relatively narrow range of individual oxide values as well as bulk compositions. XRD and SEM indicate that only one mineral is present, so it seems that it should be defined as a dioctahedral member of the smectite group, containing dominant Cr in the octahedral position. Varieties between end-member compositions should be described as, for example, chromian nontronite.-R.E.S.
Additional publication details
Reassessment of the volkonskoite-chromian smectite nomenclature problem.