Mica - Umo

X ₂ Y _4-6 [(Si,Al) ₈ O ₂₀ ](OH,F) ₄ ​​. When X = K or Na, it is called brittle mica, and when X = Ca, it is called common mica. When Y = Al, Fe, Li, or Mg, when Y is 4, it is called dioctahedral mica, and when Y is 6, it is called trioctahedral mica. It belongs to the phyllosilicate mineral, and other ions are sandwiched between the layered structure of SiO ₄ tetrahedrons. It is widely distributed in igneous, metamorphic, and sedimentary rocks. It is also synthesized on an industrial scale; for example, fluorphlogopite can be grown into large crystals by heating the components K ₂ SiF ₆ ･6MgO･Al ₂ O ₃ ･5SiO ₂ to 1000-1300 °C by self-resistance heating. It has superior heat resistance compared to naturally occurring mica. Also, due to differences in the way the layers are stacked in the crystal structure, polymorphs such as 1M type (single layer), 2M type, 2O type (two layers), 3T type (three layers), and 6H type (six layers) are known. Monoclinic plate crystals. Density 2.75-3.2 g cm ^-3 . Hardness 2.5-4. n 1.525-1.696. Muscovite, phlogopite, and safflower mica are widely used as heat-resistant insulating materials.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

X₂Y_4～6[(Si,Al)₈O₂₀](OH,F)₄．X ＝ K，Naのものを脆雲母(brittle mica)，X ＝ Caのものを普通雲母(common mica)という．Y ＝ Al，Fe，Li，MgでYが4のものをジオクタヘドラル型雲母，6のものをトリオクタヘドラル型雲母と大別する．フィロケイ酸塩鉱物に属し，SiO₄の四面体の層状構造の間にほかのイオンがはさまれている．火成岩，変成岩，たい積岩中に広く分布する．合成も工業的な規模で行われており，たとえば，フッ素金雲母(fluorphlogopite)は，K₂SiF₆･6MgO･Al₂O₃･5SiO₂の成分を自己抵抗加熱により1000～1300 ℃ に熱して大結晶を育成できる．これは天然産雲母に比べて，耐熱性にすぐれている．また，結晶構造のうえから層の積重なりの違いにより，1M型(一層)，2M型，2O型(二層)，3T型(三層)，6H型(六層)などの多形が知られている．単斜晶系板状結晶．密度2.75～3.2 g cm^－3．硬度2.5～4．n1.525～1.696．白雲母，金雲母，べに雲母などは，耐熱絶縁材料として広く利用されている．

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