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Syenite from Corsica QAPF diagram that shows the quartz (Q), alkali feldspar (A), and plagioclase (P) composition of syenite Leucocratic variety of nepheline syenite from Sweden Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite , but deficient in quartz , which, if present at all, occurs in ...
Case hardening is a weathering phenomenon of rock surface induration.It is observed commonly in: felsic alkaline rocks, such as nepheline syenite, phonolite and trachyte; pyroclastic rocks, as pyroclastic flow deposit, fine air-fall deposits and vent-filling pyroclastic deposits; sedimentary rocks, as sandstone and mudstone.
A worldwide average of the major elements in nepheline syenite tabulated by Barker (1983) is listed below, expressed as weight percent oxides. Nepheline syenite is characterized by high ratio of (Na 2 O+K 2 O)/SiO 2 and (Na 2 O+K 2 O)/Al 2 O 3, which are represented respectively by the existence of nepheline and alkaline mafic minerals ...
Baddeleyite was first found in Sri Lanka in 1892. It can be found in numerous terrestrial and extraterrestrial rocks. Some of these terrestrial rocks are carbonatite, kimberlite, alkaline syenite, some rocks of layered mafic intrusions, diabase dikes, gabbroid sills and anorthosite. [5]
Trachyte (/ ˈ t r eɪ k aɪ t, ˈ t r æ k-/) is an extrusive igneous rock composed mostly of alkali feldspar.It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, [1] and is formed by the rapid cooling of lava (or shallow intrusions) enriched with silica and alkali metals.
Shonkinite is an intrusive igneous rock.More specifically, it is a mafic foidal (feldspathoid bearing) syenite, a holocrystalline (completely crystalline) intrusive rock which, in the restricted sense [clarify], is composed of potassic feldspar (in the form of sanidine), with nepheline, augite, biotite, and olivine. [1]
Pink eudialyte in syenite from Poços de Caldas, Brazil.The white mineral is alkali feldspar, the black is aegirine, and the little brown bits are biotite.. Eudialyte, whose name derives from the Greek phrase Εὖ διάλυτος, eu dialytos, meaning "well decomposable", is a somewhat rare, nine-member-ring cyclosilicate mineral, which forms in alkaline igneous rocks, such as nepheline ...
Nepheline syenite – Holocrystalline plutonic rock – A silica-undersaturated plutonic rock of nepheline and alkali feldspar; Nephelinite – Igneous rock made up almost entirely of nepheline and clinopyroxene – A silica-undersaturated plutonic rock with >90% nepheline; Norite – Mafic intrusive igneous rock – A hypersthene-bearing gabbro