(Typomorphic features of celadonite structure.

The 1M celadonite from ferruginous metasomatic silicate rocks of the Krivoi Rog, Ukraine, has a high Fe3+ content in the octahedral layer, with a 5.21-5.23, b 9.03-9.05, c 10.10-10.15 A, beta 100o30'-100o50'. This presence of Fe3+ in the octahedral layer determines the unique structure of the dioctahedral phyllosilicates. The degree of structural perfection of celadonite is a sensitive indicator of the conditions of crystallization. -R.A.H.