ИНФРАКРАСНЫЕ СПЕКТРЫ, ПАРАМЕТРЫ ЭЛЕМЕНТАРНОЙ ЯЧЕЙКИ И ОПТИЧЕСКИЙ ЗНАК БОРСОДЕРЖАЩИХ ВЕЗУВИАНОВ И ВИЛЮИТОВ

Abstract

Collection of vcsuvianitcs with different boron content was investigated by methods of IR spcctroscopy and X-ray diffractomctry, optical properties of specimens were studied also. Boron atoms can occupy in structure of vesuvianite two sites: T(l) with tctrahcdral coordination, and T(2) - triangular or linear coordination. It has been revealed that boron in low symmetrical vcsuvianitcs (space group /M/n) occupies exactly triangular site, and in high vesuvianites (space group P4/nnc) - both T(l) and T(2) sites. These two types of boron coordination in vesuvianites and wiluitcs has been also verified by IR-spectroscopy. Participation of significant boron amount in tetrahcdra, with its common content in the sample about 2.5 a. p. f. u., leads to change in proportions of unit cell parameters: sharp increase of a and decrease of с values. Subsequently, the optical character is changing from negative in vesuvianites to positive one in wiluites.