|Mineral class||Silicates : Tektosilicates : Feldspar group.|
|Chemical formula||(Na,Ca)(AlSi3O8) (100-90% Na, 0-10% Ca)|
|Habitus||Tabular to prismatic, commonly with polysyntetic twinning. Often occuring in lamellar aggregates (cleavelandite) or as grainy aggregates (albitite).|
|Cleavage|| Perfect in one direction and good in another with 90 degrees angle.|
Often with fine striation on cleavages.
|Color||White to colorless.|
|Luster||Vitreous to pearly. Transparent to translucent.|
|Occurance||As a major part of many rocks, especially igneous rocks as granites, syenites and pegmatites.|
|Notes||Twinning often produces many layers on top of each other, each only a fraction of a mm to several mm thick. Theese layers can be seen as striations not only on the surface of the crystal, but also on cleavages. This is a characteristic sign of the plagioclase feldspar series.|
|Locations|| A very common mineral. |
| To silicate index.
|| Mineral group index.
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