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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 ...
The Red Hill syenite is a medium- to coarse-grained syenite. The six units of the Red Hill Syenite all contain primarily alkali feldspar, with many rocks displaying perthitic igneous texture. The perthites range from microperthite (lamellae barely visible or not visible to the naked eye) to very coarse exsolution textures.
Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. [1] The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites , but dark green varieties are also known.
It is a coarse-grained, foliated variety of nepheline syenite, [1] sometimes called nepheline syenite gneiss or gneissic nepeheline syenite. [2] Litchfieldite is composed of two varieties of feldspar (mostly albite but also some microcline ), with nepheline , sodalite , cancrinite and calcite .
A notable exception where feldspathoids and quartz-bearing rocks are found together is the Red Hill Syenite. [ 1 ] Foid , a contraction of the term feldspathoid , is applied to any igneous rock containing up to 60% modal feldspathoid minerals.
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 ...
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.
The Coldwell Complex is a large circular gabbro and syenite intrusion within the Earth's crust. Located on the North Shore of Lake Superior in Ontario , Canada , it is the largest alkaline intrusion in North America with a diameter of 25 km (16 mi).