Phlogopite, KMg3

The potassium ions are located between the flat aluminosilicate sheets (Fig. 7.4). Crystals of micas cleave easily parallel to the sheets, and the thin transparent flakes can be used for electrical insulation (e.g., in capacitors) or as furnace windows. Phlogopite, KMg3(OH)2[Si3A10io], has a similar structure but with Mg2+ in octahedral environments instead of Al3+. 

Type II (TOT) silicates include pyrophyllite, AlSi2Os(OH) (Section 10.3.25) and talc, Mg3Si40io(OH)2 (Section 10.3.24). Muscovite, KAl2(AlSi3)Oio(OH)2 (Section 10.3.27), and phlogopite, KMg3(Si3Al)Oio(F, OH)2 (Section 10.3.28) are Type II minerals with K+ ions in interlayer sites. 

The Crystal Structure of Phlogopite [KMg3(Si3Al)Oi0F2]... 

Muscovite KAl2(AlSi30,o)(OH)2 Phlogopite KMg3(AlSi30,o)(OH)2 Biotite K(Mg,Fe)3(AlSi30,o)(OH)2... 

In the same way, a series of micas can be derived from talc, e.g. phlogopite, KMg3(Si3Al)Oio(OH)2. Lepidolite, K(AlLi2)Si40io(OH)2, mentioned in the section on fluxes, also falls into this group, and is an example of substitution in the gibbsite layer. 

Phlogopite KMg3(AiSi30,o)(OH,F)2 M,H True Madagascar, Canada, Mexico, Sri Lanka... 

Mica Phlogopite KMg3(AlSi30io)(OH)2 Monoclinic Transparent In thin sheets... 

Phyllosilicates Continuous sheets of tetrahedral each sharing three oxygens 2 5 Talc, Mg3Si40,o(OH)2 Phlogopite, KMg3 (AlSi30,o) (0H)2... 

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