2.1.3. [6] It also occurs on Pikes Peak, El Paso County, Colorado. Residual biotite patches have higher birefringence. Occurrence The examined ilmenite and wangdaodeite occur as clasts in a shock melt vein in a xenolith of garnet-sillimanite-cordierite restite (thin section c of specimen ZLN114 [13]) that was found in suevite Biotite. 13 images. It has a chemical formula of KFe 3 2+ AlSi 3 O 10 (OH,F) 2. biotite mineralbiotite mineral; biotite mineral; Biotite is the most common mica mineral and also known as black mica, a silicate mineral in the common mica group.Approximate chemical formula K (Mg, Fe). In this photo the thin section was rotated to obscure twinning. Notice the concentric layers (zones) of inclusionsl. Some of the larger crystals can be seen here to have first order birefringence. Hazen, R.M. This isotropic mineral has much lower relief than both garnet and fluorite, and its refractive index is closer to alkali feldspars and epoxy than either. It has two endIt has two end-members: Phlogopite (Mg) and Annite (Fe).members: Phlogopite (Mg) and Annite (Fe). Andalusite in hand sample (clicking on some images leads to larger versions) Andalusite (chiastolite) from a graphitic schist, Hamadan, Iran. In this view, healed fractures are highlighted by minute birefringent grains. Titanite birefringence is very high, making it difficult to determine interference color order from the high-order pastel interference colors normally seen. (1981) Geology and genesis of the F-Sn-W(-Be-Zn) skarn (wrigglite) at Moina, Tasmania. Trust but verify: the value of acceptance testing. The Kaydon Reali-Slim® inch-standard bearing is one of the most widely used thin section bearings in the world. annite definition: Noun (plural annites) 1. See Photos. Damage produced during thin section grinding causes speckles of light in the biotite, where the crystal lattice has been deformed. Orthoclase in a dacite hypobyssal intrusive. In optical mineralogy and petrography, a thin section (or petrographic thin section) is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe. The chlorite mostly has an anomalous brown low first order interference color, indicative of Mg-rich chlorite. Grains with the cleavages E-W have the least absorption (not shown in this image). Damage produced during thin section grinding causes speckles of light in the biotite, where the crystal lattice has been deformed. Birefringence in the low to middle first order. Aegirine (Na–Fe3+ monoclinic pyroxene), alkaline granite. Notice how the twin domains are spindly and somewhat wispy. The largest grain of biotite contains a pelochroic halo (burn mark) around an included zircon. In cross-polarized light you can see that the zones also have different birefringence, indicating they have different anorthite content. At high magnification, the magenta bands can be counted up a thin edge to get a better idea of the interference order. Calcite in an alkaline granite. Each thin section was first scanned in unpolarized light and then again between two sheets of crossed polaroid film aligned parallel to the thin section edges. The fluorite here is primary, as it occurs as euhedral and subhedral single crystals in a relatively fine-grained matrix. [7], Annite is a member of the mica group and has very similar properties as other micas such as muscovite and biotite. Third, or even 4th order birefringence (i kdbill)(sometimes masked by mineral colour) Annite= KFe 3 AlSi 3 O 10 (OH) 2. CiteSeerX - Scientific documents that cite the following paper: Nonideal mixing in the phlogopite-annite binary: Constraints from experimental data on Mg- Fe partitioning and a reformulation of the biotite-garnet geothermometer: Contributions to Mineralogy and Petrology Though it may seem obvious, opaque minerals are opaque in plane- and cross-polarized light, which differentiates them from isotropic, transparent minerals. Accessibility Help. Small residual brownish patches of biotite still occur, as do dark bits of titanite. Chromite is dark-brown to opaque at full thin section thickness.
annite thin section
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