Mineral description : Gahnite

Dark blue gahnite in an anthophyllite - mica matrix. From Näverbergsgruvan, Falun.

Mineral class Oxides : Corundum - Spinell - Chrysoberyll group
Chemical formula ZnAl2O4
Crystal system Cubic
Habitus Crystals octaedric, sometimes as cubes or dodecahedrons. Twinning according to the spinel twin law could create pseudo trigonal crystals. Common as massive or grains.
Cleavage None, fracture conchoidal.
Hardness 7.5-8
Density 4.55-4.60
Color Dark gray, dark blue, green, brown, yellow.
Streak Gray
Luster Vitreous, translucent to opaque.
Description A rare spinell mineral.
Occurance  
Associates Calcite, garnets, anthophyllite.
Notes Type locality : Falun, Sweden.
Locations A rare mineral with several good crystal localities in Sweden.
  • Falu mine, Dalarna. As ark gray octaedric crystals up to a couple of cm in size.
  • Näverbergsgruvan, Falun, Dalarna. As blue green rounded grains with anthophyllite.
  • Östra Silfberg, Ludvika, Dalarna.
  • Garpenbergsgruvan, Dalarna.
  • Kobergsgruvan, Persberg, Värmland.
  • Kaveltorpsgruvan, Ljusnarsberg.

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Last changed : 1999-01-08