Mineral description : Margarite

Margarite as a thin rim around a corundum crystal in andesine. The rock comes from an anorthosite. From Södra yxesjön, Värmland.

Mineral class Silicates : Mica group
Chemical formula CaAl2(Al2Si2)O10(OH)2
Crystal system Monoclinic
Habitus Foliated micaceous aggregates with up to 3 cm sheets or massive. Rarely as thin pseudohexagonal tabular crystals.
Cleavage Perfect {001}, sheets brittle fracture.
Hardness 3.5 - 4.5
Density 2.99-3.08
Color Grayish, pale pink, yellow to green.
Streak White
Luster Vitreous, pearly on cleavage, translucent.
Description  
Occurance In low and medium-grade metamorphic rocks. In chlorite and mica schists.
Associates Corundum, diaspore, tourmaline, staurolite, glaucophane, chlorite, magnetite, spinel, andalusite, calcite, quartz.
Notes Sometimes formed as an alteration product of corundum.htm.
Localities A not so common mineral in Scandinavia.
Sweden : Some localities known
  • Tvärå, Torsby, Värmland.
  • Västra Frölunda, Göteborg, Bohuslän.
  • Södra Yxesjön, Eda, Värmland.
Norway : Some localities known
  • Kongsfjell area, Bleikvatnet, South of Mo i Rana. In contact zone between clinozoisite and corundum.
  • Duestöl and Almklovseter, Sunnmöre. As bands in eklogites.
  • Seljenes, Nordpoll, Selje. As up to 5 cm nodules in a labradorite.
  • Duestöl, Bergen-field. Light red margarite in muscovite aggregates in a metamorphosed anorthosite.
  • Selje / Almklovdal area. As a major constituent of metamorphosed anothosites.
  • South Kalskaret, Tafjord. Small amounts of margarite in corundum nodules in an anorthosite layer.
Finland : At least one locality
  • Juurakko pegmatite, Orivesi, Southern Finland. Pseudomorphs after topaz.

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Last changed : 2000-10-15