**1. Crystal Chemistry of Minerals and Their Synthetic Analogs**

Gurzhiy et al. [1] reviewed the crystal chemistry of the family of natural and synthetic uranyl selenite compounds, paying special attention to the pathways of synthesis and topological analysis of the known crystal structures. Crystal structures of two minerals were refined. The H atoms positions belonging to the interstitial H2O molecules in the structure of demesmaekerite, Pb2Cu5[(UO2)2(SeO3)6(OH)6](H2O)2, were assigned. The refinement of the guilleminite crystal structure allowed the determination of an additional site arranged within the void of the interlayer space and occupied by an H2O molecule, which suggests the new formula of guilleminite to be written as Ba[(UO2)3(SeO3)2O2](H2O)4. This paper could be regarded as the first review on the mineralogy and crystal chemistry of the named group of compounds.

Tyumentseva et al. [2] studied the alteration of the uranyl oxide hydroxy-hydrate mineral schoepite [(UO2)8O2(OH)12](H2O)12 at mild hydrothermal conditions in the presence of sulfate oxyanions, which resulted in the crystallization of three novel compounds.

Comparison of the isotypic natural and synthetic uranyl-bearing compounds [1,2] suggests that formation of all uranyl selenite and of the majority of uranyl sulfate minerals requires heating, which most likely can be attributed to the radioactive decay. The temperature range could be assumed from the manner of the interpolyhedral linkage.
