Pegmatite
The pegmatite is a magmatic Roche with large crystals of size higher than 20 mm, and being able to reach several meters
The majority of pegmatites have a granitic composition. They contain usually quartz, Feldspath S and Mica. Other minerals can exist: Tourmaline, topaz, Beryl, Garnet-red, Wolframite, Apatite, etc with sometimes of rare minerals like some Phosphate S of iron or of the niobo - tantalates.
Pegmatites form pockets or seams, inside or with the immediate vicinity of let us plutons granitic with which, they are genetically associated. They correspond to the residual liquid, rich in water, of end of crystallization of a granitic magma. The abundance of water facilitates the diffusion of the chemical elements and allows the growth of the large crystals.
Layer
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