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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.
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 ...
Phonolite is an uncommon shallow intrusive or extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous rock trachyte that contains nepheline or leucite rather than quartz. [1]
Nepheline, also called nephelite (from Ancient Greek νεφέλη (nephélē) 'cloud'), is a rock-forming mineral in the feldspathoid group – a silica-undersaturated aluminosilicate, Na 3 K Al 4 Si 4 O 16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites.
The term porphyry is from the Ancient Greek πορφύρα (porphyra), meaning "purple". Purple was the colour of royalty, and the Roman "imperial porphyry" was a deep purple igneous rock with large crystals of plagioclase. Some authors claimed the rock was the hardest known in antiquity. [3]
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 ...
UCLA, South Carolina, Texas and Notre Dame would be the No. 1 seeds in the women's NCAA Tournament if it began now. The NCAA basketball selection committee on Sunday did its first reveal of the ...
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 .