by Dmitry Demezhko, Institute of Geophysics UB RAS, Yekaterinburg, Russia
Liesegang rings in volcano-sedimentary rock. Polished sample 15x9 cm. It was found in the Gobi Desert, Mongolia, in 1983.
“The precise mechanism from which Liesegang rings form is not entirely known and is still under research, however there is a precipitation process that is thought to be the catalyst for Liesegang ring formation referred to as the Ostwald-Liesegang supersaturation-nucleation-depletion cycle” (from Wikipedia)
Dmitry Demezhko (distributed via imaggeo.egu.eu)