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.

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.
Streak
Luster	Vitreous, pearly on cleavages. Transparent to translucent.
Description
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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