Topaz (mineral)

According to the Roman naturalist Pliny the Elder, the name topaz comes from the island of Topazos (probably St. John's Island), located in the Red Sea. In fact, however, it was not topaz that was mined there, but olivine, which was long confused with topaz. Another explanation traces the name back to the Sanskrit word tapas, which means "fire" or "glow".

In 1740, a topaz known as the Braganza diamond was placed in the Portuguese crown in the belief that it was a genuine diamond.

Already in the meanwhile outdated, but still common 8th edition of the mineral systematics according to Strunz the topaz belonged to the mineral class of the "silicates and germanates" and there to the division of the "island silicates with anions foreign to the tetrahedron (Neso-subsilicates)", where it formed as eponym the "topaz group" with the system no. VIII/B.02 and the further members andalusite, boromullite, kanonaite, krieselite, kyanite, mullite, sillimanite and yoderite.

The 9th edition of Strunz's mineral systematics, valid since 2001 and used by the International Mineralogical Association (IMA), also classifies topaz in the division of "isosilicates (nesosilicates)". However, this is further subdivided according to the crystal structure, so that the mineral is to be found according to its structure in the subdivision "island silicates with additional anions; cations in [4]er, [5]er and/or only [6]er coordination", where it forms only together with krieselite the "topaz group" with the system no. 9.AF.35.

The system of minerals according to Dana, which is mainly used in English-speaking countries, also classifies topaz in the class of "silicates" and there in the division of "insular silicates: SiO4 groups and O, OH, F and H2O". Here it is to be found as eponym of the "topaz group" with the system no. 52.03.01 and the further member krieselite within the subdivision of the "island silicates: SiO4 groups and O, OH, F and H2O with cations only in [6] coordination".