Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
Topaz (Al2SiO4(OH,F)2) is an aluminosilicatewith one oxygen replaced by two hydroxyl or fluorine atoms. The structureconsists of close-packed layers in an ABAC stacking. Zigzag aluminum octahedralchains are joined by silica tetrahedra. In the polyhedral models below, the redspheres denote hydroxyl or fluorine. The first model shows the zigzag chains,the second a larger piece of the structure.
The ball model below shows a single oxygen layer (blue) with aluminum(yellow) and silicon (purple) cations.
The ball model below shows several layers of the structure. Oxygen is shownin shades of blue, hydroxyl or fluorine in green, aluminum in yellow and siliconin purple.
Created 22 February, 2001, Last Update 31 May 2020