Phlogopite structure

Figure 2 (right). Schematic detail of the phlogopite structure illustrating calculated atomic motions for the IR active B mode at 408 cm according to McKeown et al. (1999). The diagram in the upper and lower part corresponds to c-axis and b-axis projections, respectively. Arrows are drawn to scale, indicating the relative amplitude of the motion for each atom... 

Figure 3-18 c-axis projection of a calculated phlogopite structure with tetrahedral rotation of a = 20. ... 

Silicates with layer. structures include some of the most familiar and important minerals known to man, partieularly the clay minerals [such as kaolinite (china clay), montmorillonite (bentonite, fuller s earth), and vermiculite], the micas (e.g. muscovite, phlogopite, and biotite), and others such as chrysotile (white asbestos). 

Hazen R. M. and Burnham C. W. (1973). The crystal structure of 1 layer phlogopite and annite. 

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+. 

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

Most of the trioctahedral tme-mica stmctures are M polytypes and a few are 2Mi, 2M2, and 3T polytypes. In dioctahedral micas, the 2Mi sequence dominates, although 3T and M structures have been found. Brittle mica crystal-structure refinements indicate that the IM polytype is generally trioctahedral whereas the 2Mi polytype is dioctahedral. The 10 structure has been found for the trioctahedral brittle mica, anandite (Giuseppetti and Tadini 1972 Filut et al. 1985) and recently was reported for a phlogopite from Kola Peninsula (Ferraris et al. 2000). The greatest number of the reported structures were refined from single-crystal X-ray diffraction data, with only a few obtained from electron and neutron diffraction experiments. 

Hazen RM, Burnham CW (1973) The crystal structures of one-layer phlogopite and annite. Am Mineral 58 889-900... 

In Table 3, the compressibility of the lattice parameters and of the polyhedral building units are reported, along with other structural parameters useful to understand the high-pressure behavior of Cs-annite, Rb-annite and phlogopite. The points outlined below show the effect of how different structural units of trioctahedral micas relate with one another, and then respond as a whole to pressure ... 

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