• Gunter Meelis (Blue Topaz)
    Properties, Crystal Structure and Morphology
    Topaz - Information
    Topaz (ExtraLapis)
    Topaz Crystal
    Topaz - Crystal Model

Topaz Description.

Properties, Structure and Morphology.

The description of topaz is mainly based on information taken from the "Lehrbuch der Mineralogie" by Hans Jürgen Rösler

Chemical formula: Al2 (F,OH)2 [SiO4]

Name: most likely the name comes from "Topazios", an old Greek name for an island in the Red Sea

Crystal structure: orthorhombic, space group Pbnm, nesosilicate, aside SiO4-tetrahedra the structure contains zigzag-chains of edge-linked Al-octahedra


Crystal Structure of Topaz

Topaz - Crystal Structure

The representation of the crystal structure is provided for information purposes only and is based on the CIF-file, which contains all parameters as result of the structure analysis performed by Wunder et al.:

Wunder B, Rubie D C, Ross C R, Medenbach O, Seifert F, Schreyer W American Mineralogist 78 (1993) 285-297

Synthesis, stability, and properties of Al2SiO4(OH)2: A fully hydrated analogue of topaz

All single views were created by use of Vesta:

K. Momma and F. Izumi, "VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data," J. Appl. Crystallogr., 44, 1272-1276 (2011).


Physical Properties of Topaz:

Colors: Colorless, Yellow, Orange, Pink, Red, Violet, Blue, Green

Luster: Vitreous (Glassy)

Hardness: 8

Specifiv Gravity (g/cm³): 3.5 - 3.7

Cleavage: perfect parallel to the basal plane (001)

Optik: birefringent, Δ=0,010, biaxial positive


Topaz - Morphology

Topaz crystals are often idiomorphic and may contain numerous faces

Here some topaz crystals of different habit (created with Vesta) and some photographs of topaz crystals