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Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula K(Mg,Fe) 3 AlSi 3 O 10 (F,OH) 2. It is primarily a solid-solution series between the iron - endmember annite , and the magnesium -endmember phlogopite ; more aluminous end-members include siderophyllite and eastonite .
The British Geological Survey (BGS) and the International Union of Geological Sciences (IUGS) both use gneiss as a broad textural category for medium- to coarse-grained metamorphic rock that shows poorly developed schistosity, with compositional layering over 5 millimeters (0.20 in) thick [2] and tending to split into plates over 1 centimeter ...
Quartz diorite is an igneous, plutonic rock, of felsic composition, with phaneritic texture. Feldspar is present as plagioclase (typically oligoclase or andesine) with 10% or less potassium feldspar. Quartz is present at between 5 and 20% of the rock. Biotite, amphiboles and pyroxenes are common dark accessory minerals. [1]
Quartz (SiO 2) is present as more than 20% of the total quartz-alkali feldspar-plagioclase-feldspathoid content of the rock. [1] [2] Amphiboles and biotite are common in lesser quantities, while accessory minerals include apatite, magnetite and zircon. [3] [4] In older references tonalite is sometimes used as a synonym for quartz diorite.
We need more info about gneiss in the Infobox. If anyone has more info about gneiss that could be added to the Infobox, please add it to the Infobox.Punk4orchrist 17:57, 13 January 2015 (UTC) Gneiss is a rock type; the infobox you want is template:Infobox rock. Vsmith 19:16, 13 January 2015 (UTC)
Latite is an igneous, volcanic rock, with aphanitic-aphyric to aphyric-porphyritic texture. It is the volcanic equivalent of monzonite . Its mineral assemblage is usually alkali feldspar and plagioclase in approximately equal amounts.
3.4 Ga. The oldest Peninsular Gneiss found in areas in the Hosur – Gorur – Holenarsipur – Hunsur belt 3.3–3.2 Ga. The second generation Peninsular Gneiss found in the Bengaluru– Chickmagalur –Holenarsipur region 3.0–2.9 Ga a) Grandiorite facies in the Bengaluru Gneisses established by the Single Zircon Kober evaporation 207 Pb ...
The different chemical types are almost impossible to distinguish even by optical or X-ray methods, and detailed chemical analysis using an electron microprobe is required. [ 11 ] There is a solid solution series between hornblende and the closely related amphibole minerals, tremolite – actinolite , at elevated temperature.