A new compound of the (K,Na)3Ca8Si6[Si4O12]3 charoite substrate
As a result of experimental studies on the interaction between a charoite substrate and host lamprophyres of microcline-arfvedsonitic composition, a new (K,Na)3Ca8Si6[Si4O12]3 compound has been obtained with a new type of radical Si2[Si4O12] found in its crystalline structure а = 15.2613 (3) Å, I2/13, Z = 4. The chain-shaped Ca-octahedra connected through common faces encircle a radical and close in a K-octagon. In contrast to charoite with banded-tube radicals, an isometrically-island silicon radical is identified.