- © The Mineralogical Society Of America
Investigations and syntheses of meso- and microporous sulfides and selenides received in general much less attention than those of silicate and oxide families. Moreover, data on such compounds are scattered over sizable literature and it is very difficult to give a qualified overview of the subject. Scanning potential candidates in crystal structure databases leads in most cases to chain and layer structures, usually with only one or two microporous and a rare mesoporous structure in the entire list of compounds with the given promising three-element combination involving a large cation, an octahedral, tetrahedral or linear cation and an anion. In this situation, the present review presents a set of outstanding examples, preferably of smaller or larger structural families, rather than a systematic list of all cases published, synthesized or investigated. Compounds and families based on inorganic framework modifiers and those related to naturally occurring compounds have preference. For crystal-chemical reasons, they are divided into a category of sulfosalts and that of complex sulfides/selenides/ arsenides without the lone-electron pair metalloids participating in the structure.
SULFOSALTS: GENERAL FEATURES
Sulfosalts are complex sulfides/selenides in which formally trivalent lone-electron pair metalloids As3+, Sb3+ and/or Bi3+ are combined with different cations: in a half of natural sulfosalt species it is Pb2+, furthermore Cu, Ag, Fe, Tl, Mn, Sn and other, less frequently occurring elements. Rare natural finds and a plethora of synthetic products by a number of research groups enlarge this spectrum of compositions with sulfosalts of Li, Na, K, Rb, Cs, as well as with those of the entire spectrum of alkaline earths and lanthanoids, and with a number of sulfosalts that contain (NH4)+ and organic cations of various sizes. Li emulates Cu in sulfosalts (ionic conductivity), Na is a fairly small cation as also is Ca. However, potassium appears …