星叶石族矿物的晶体化学

星叶石是碱性岩中分布较广泛的副矿物,成分富含碱金属K、Na及Ti,随其产出的地球化学条件,类质同象代换情况较复杂,形成许多成分异种。本工作之前对其组成和性质都不十分清楚,前人虽进行了一般矿物学研究,但未能确定所属晶系,B.C.索波列夫曾推断星叶石中Ti呈四面体配位,并与硅氧四面体组成复杂构造。

THE CRYSTAL CHEMISTRY OF ASTROPHYLLITE GROUP MINERALS

Astropllyllite is an accessory mineral in alkaline rocks and is a sheeted titanosilicate. In present work two kinds of structures of astropllyllite are identified: the structure of monoclinic magnesium astrophyllite K2Na2 (Fe, Mn)5Mg2Ti2 Si4O12]2 (O,OH)3 (OH,F)4 and the trilinic manganoan astrophyllite (K, Na)2(Fe, Mn)7Ti2Si4O12]2(O,OH)3(OH,F)4 and a new mineral, hydro-astrophyllite was found (K, Ba, H3O)2 (Na, CaH3O)... (Fe, Mn, Mg)5.773 (Ti, Nb, Ta)1.859 (Si, Al)5.801 OH6.596 O17.404 (O,OH,F).In the determination of the crystal structures, a new type of Si-O chains Si4 O12]n8n- was found which is called astrophyllitie bauded Si-O chain.The isomorphism of astrophyllite group minerals was studied and the controlling factors of polymorphism of the astrophyllite group minerals was discussed. The crystal chemistry of the sheeted titano-silicates was inducted and the two functions of titanium in crystsl chemistry were proposed.