Mineral description : Topaz

Picture pending, topas from Viitaniemi, Finland.
Topaz from Viitaniemi pegmatite, Finland.
Topaz from Viitaniemi pegmatite, Finland.

Mineral class Silicates : Nesosilicates : Topas - staurolite group
Chemical formula Al2(F2/SiO4)
Crystal system Orthorombic
Habitus As prismatic crystals with rombic crossection. Vertically striated prism surfaces.
Cleavage Basal perfect. Fracture conchoidal to irregular.
Hardness 8
Density 3.49
Color Nuances in yellow, blue or pink. Transparent to translucent.
Streak White
Luster Glas.
Description  
Occurance In granitic ( especially greissen and clevlandite) pegmatites, ryolite and quartz dykes. Also as grains in granites that have been altered by solutions containing fluoride.
In hydrothermal veins of high temperature type.
Associates Fluorite, turmaline, apatite, beryll and cassiterite.
Notes Very hard. Can be found in alluvial deposits.
Clear crystals are used as gemstones, where the orange-brown is the most valuable one.
Variants Phyrophysalite - As massive pieces or raw crystals with mica transformed surfaces.
Pyknite - is a radiating ????(strålig) type of topas.
Locations There is no known locality of topas in gem quality in Sweden. However there are a couple of locations with the pyrophysalite variant in Sweden.
  • Väne Ryrs quartz quarry, outside Vänersborg. Up to 1 dm long crystals, often with coarse lepidolite.
  • Finnbo and Kårarvet in the vicinity of Falun, Dalarna. Coarse crystals coated with mica.
  • Stripåsen quartz quarry near Norberg, Västmanland. Big crystals ( up to 1m length) heavily transformed into mica.
  • Ultevis, Juoråive in the Laplandic fjells. Up to 1 dm white-grey crystals together with beryl.
  • Also in Kolsva feldspar quarry and some quartz quarries around Långban.
  • Viitaniemi pegmatite Finland.
  • Elverum, Norway. In a kyanite quartsite with up to 18% topas. Together with lazulite, rutil, svanbergite, and pyrite.
  • Iveland, Norway. In numerous cleavelandite pegmatites together with beryl, (yttro-)flourite, mikrolite, tantalite...
  • Topase crystals are known from Heskestad, Vegusdal, Kragerö, Modum, Nesodden, Östfold and Drag (all in Norway).
  • Tördal, Norway. As coarse and cracked crystals and masses from Höydalen and Skarsfjell.
  • Mökster, Norway. As clear grains in a granite lens.
  • Hurumlandet, Norway. As perfect, clear crystals or as blue coarser crystals. These are the best topase crystals from Norway.

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Last changed : 1998-03-07