Tischendorf, G., Rieder, M., Förster, H.-J., Gottesmann, B., Guidotti, Ch. V. (2004) A new graphical presentation and subdivision of potassium micas. Mineralogical Magazine, 68 (4) 649-667 doi:10.1180/0026461046840210
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | A new graphical presentation and subdivision of potassium micas | ||
| Journal | Mineralogical Magazine | ||
| Authors | Tischendorf, G. | Author | |
| Rieder, M. | Author | ||
| Förster, H.-J. | Author | ||
| Gottesmann, B. | Author | ||
| Guidotti, Ch. V. | Author | ||
| Year | 2004 (August) | Volume | 68 |
| Page(s) | 649-667 | Issue | 4 |
| Publisher | Mineralogical Society | ||
| DOI | doi:10.1180/0026461046840210Search in ResearchGate | ||
| Mindat Ref. ID | 243562 | Long-form Identifier | mindat:1:5:243562:0 |
| GUID | 5d33d0d4-f239-4618-8f80-923e3f9d9b41 | ||
| Full Reference | Tischendorf, G., Rieder, M., Förster, H.-J., Gottesmann, B., Guidotti, Ch. V. (2004) A new graphical presentation and subdivision of potassium micas. Mineralogical Magazine, 68 (4) 649-667 doi:10.1180/0026461046840210 | ||
| Plain Text | Tischendorf, G., Rieder, M., Förster, H.-J., Gottesmann, B., Guidotti, Ch. V. (2004) A new graphical presentation and subdivision of potassium micas. Mineralogical Magazine, 68 (4) 649-667 doi:10.1180/0026461046840210 | ||
| Abstract/Notes | AbstractA system based on variation of the octahedrally coordinated cations is proposed for graphical presentation and subdivision of tri- and dioctahedral K micas, which makes use of elemental differences (in a.p.f.u.): (Mg – Li) [= mgli] and (Fetot + Mn + Ti – VIAl) [= feal]. All common true tri- and dioctahedral K micas are shown in a single polygon outlined by seven main compositional points forming its vertices. Sequentially clockwise, starting from Mg3 (phlogopite), these points are: Mg2.5Al0.5, Al2.167□0.833, Al1.75Li1.25, Li2Al (polylithionite), Fe22+Li, and Fe32+ (annite). Trilithionite (Li1.5Al1.5), Li1.5Fe2+Al0.5, Fe22+ Mg, and Mg2Fe2+ are also located on the perimeter of the polygon. IMA-siderophyllite (Fe2+2Al) and muscovite (Al2□) plot inside.The classification conforms with the IMA-approved mica nomenclature and differentiates among the following mica species according to their position in a diagram consisting of mgli and feal axes plotted orthogonally; trioctahedral: phlogopite, biotite, siderophyllite, annite, zinnwaldite, lepidolite and tainiolite; dioctahedral: muscovite, phengite and celadonite. Potassium micas with [Si] <2.5 a.p.f.u. including IMA-siderophyllite, KFe22+ AlAl2Si2O10(OH)2, and IMA-eastonite, KMg2AlAl2Si2O10(OH)2 seem not to form in nature.The proposed subdivision has several advantages. All common true, trioctahedral and dioctahedral K micas, whether Li-bearing or Li-free, are shown within one diagram, which is easy to use and gives every mica composition an unambiguously defined name. Mica analyses with Fe2+, Fe3+, Fe2+ + Fe3+, or Fetot can be considered, which is particularly valuable for microprobe analyses. It facilitates easy reconstruction of evolutionary pathways of mica compositions during crystallization, a feature having key importance in petrologically oriented research. Equally important, the subdivision has great potential for understanding many of the crystal-chemistry features of the K micas. In turn this may allow one to recognize and discriminate the extent to which crystal chemistry or bulk composition controls the occurrence of some seemingly possible or hypothetical K mica. | ||
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