Mica bookMost mineralogy class collections around the world have a specimen like this: a book of mic

Mica bookMost mineralogy class collections around the world have a specimen like this: a book of mica, typically the specific mineral muscovite.Mica minerals are sheet silicates. These minerals have strong chemical bonds holding them together and extending out in 2 directions and weak chemical bonds in the third direction, causing the formation of a single dominant cleavage plane surface.Literally, mica minerals stack up like sheets in a book. They can be peeled off one sheet at a time and large enough sheets can even be used industrially to cover open gaps.This mica book comes from a pegmatite deposit in the Russian Ural Mountains. Pegmatites are the last dregs of the crystallization of large magma bodies. When magma bodies crystallize, they form common minerals like quartz and feldspar, but components like water and some minor elements don’t go into those minerals and just stay in this last-gasp fluid. Those fluids are hot and mineral loaded, allowing them to grow very large mineral grains and providing some of our most impressive mineral samples. This mica book has grown along with the mineral topaz from the same fluid.-JBBImage credit: http://commons.wikimedia.org/wiki/File:Topaz-Muscovite-189213.jpgRead more:http://geology.com/rocks/pegmatite.shtml -- source link

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