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Download hereGENERAL DESCRIPTION
Albite is a sodic feldspar, therefore a sodium aluminosilicate. It forms, with anorthite, the two extremes in composition of a series of minerals which one calls "plagioclases" (anorthite being a calcic feldspar).
White feldspar is one of the principal components of diorites, andesites, some granites and pegmatites.
The crystals are tabular, of white to gray colour. Besides, white feldspar draws its name from Latin "albus" which means "white". The repetition of simple twins (twin known as "polysynthetic") is widespread, one will easily observe the habit thanks to a microscope with a polarized light.
The cleavelandite is a variety of white feldspar that presents pure crystals, flat and lamellate. It is a species usually associated tourmalines or muscovite in the most exceptional pegmatites.
White feldspar is a very widespread mineral, its deposits are numerous: Afghanistan, Australia, Austria, Brazil, Canada or China. In France: massif of the Lauzière in Savoie; Saint-Véran in Hautes-Alpes; Saint-Christophe in Oisans in Isère, to quote only a few of them. White feldspar is used out of ceramics for its melting capacity, it melts around 1270 °C.
The type of this very important species (published in 1821 by Gahn and Berzelius) is kept in the Haüy collection at the Muséum national d’Histoire naturelle in Paris (sample H 6727). This sample was offered by Jöns Berzélius and comes from Sweden (mine of Finnbo with Falun, area of Kopparberg).
HISTORY : Name derived from Latin "albus" meaning white, Name given for its color
Species first described in 1815 by Johan Gottlied Gahn (1745-1818) and Jöns Jacob Berzélius (1179-1848), Swedish chemists
Type-locality: Finnbo, Kopparberg, Suède
CHEMICAL FORMULA : Na Al Si3 O8
CRYSTAL SYSTEM : Triclinic
COLOR : White to gray, greenish, blueish
DIAPHANIETY : Transparent to translucent
LUSTER : Vitreous to pearly
STREAK : White
MORPHOLOGIE : Crystals often tabular
HARDNESS : 6,0-6,5
CHEMICAL CLASS: 2,609-2,62
DENSITY : VIII - Silicates
GROUP : Feldspath plagioclase
STRUNZ CLASS BEFORE 2001 : 8/J.07-20
STRUNZ CLASS AFTER 2001 : 9.FA.25
