Mineral description : Hornblende

Massive grainy aggregate of hornblende with pyrite from Bäckegruvan.
Hornblende in a pegmatite from Västerås.

Mineral class Silicates : Inosilicates : Hornblende group.
Chemical formula Ca2(Mg,Fe)4Al(Si7Al)O22(OH,F)2
Crystal system Monoclinic.
Habitus Prismatic crystals, often with hexagonal cross section and twinning. Also in massive, fibrous, bladed, columnar, and granular aggregates.
Cleavage Perfect in two directions along the crystal with an angle of 60 or 120 degrees between cleavages. Fracture uneven.
Hardness 5-6
Density 3.28-3.41
Color Black, green or greenish brown.
Streak White or gray.
Luster Vitreous, translucent to opaque.
Occurance In igneous rocks. Also in metamorphic rocks as amphibolite and schist.
Notes Fuses with difficulty.
Insoluble in acids.
Locations A very common mineral in Sweden.
  • Kärrgruvan, Tunaberg. As crystals.
  • Kaveltorpsgruvan, Kopparberg. As crystals.
  • Persberg mining district, Värmland. As crystals.
  • Nordmark mining district, Värmland. As crystals.
  • Lindbo limestone quarry, Lindesberg. As crystals.
  • Malmberget, Norrbotten. As crystals.
  • ... and many more localities.

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Last changed : 1998-09-12