Mineral description : Petalite

Petalite from Varuträsk.
Showing side with cleavage.
Petalite from Varuträsk.
Showing side without cleavage.
Petalite in fine grained mica from Varuträsk. Note the border of montmorillonite along the edge.
Large piece of petalite from Varuträsk. The specimen consists of two crystals without crystal surfaces, intergrown in an angle.
Specimen size 10x5x3 cm.

Mineral class Silicates : Tektosilicates : Nefeline - Leucite - Sodalite group.
Chemical formula LiAlSi4O10
Crystal system  
Habitus Most commonly in cleavable masses without crystal form.
Cleavage Perfect in one plane, fracture subconchoidal.
Hardness 6.5
Density 2.4
Color Gray to weeakly reddish gray.
Luster Vitreous, pearly on cleavages. Transparent to translucent.
Occurance In lithium pegmatites.
Associates Spodumen and other lithium minerals.
Notes Easy to separate from feldspar since it only have one cleavage.
Locations A less common mineral with two good localities.
  • Varuträsk, Västerbotten. As large cleavable masses without any crystal faces. Often transfered into pink montmorillonite on the surface and in fractures.
  • Utö, Stockholm archipelago.

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Last changed : 1998-06-18