What is the composition of nepheline syenite?
Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. 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….Nepheline syenite.
| Composition | |
|---|---|
| Secondary | magnetite, ilmenite, apatite, titanite |
What is the volcanic equivalent of nepheline syenite?
phonolite
Nepheline syenite is a pale-colored, coarse-grained rock composed essentially of alkali feldspar (ca. 70%) and nepheline (ca. 20%) with minor proportions of dark minerals such as sodic pyroxene, sodic hornblende, or biotite; its volcanic equivalent is phonolite.
What is the use of nepheline syenite?
The material is used in ceramic glazes and enamels and in fillers in paints, papers, plastics and foam rubber. In Canada, about two-thirds of nepheline syenite is consumed by the glass industry for containers, flat glass, insulating fibreglass and textile glass fibre. Nepheline syenite is extracted from open pit mines.
Where can nepheline syenite be found?
Nepheline Syenite is an anhydrous sodium potassium alumino silicate. Although feldspar-like in its chemistry, mineralogically it is an igneous rock combination of nepheline, microcline, albite and minor minerals like mica, hornblende and magnetite. It is found in Canada, India, Norway and USSR.
How is nepheline formed?
Nepheline only forms in silica-poor rocks. It is almost never associated with quartz. It may be found in some contact metamorphosed rocks otherwise it occurs in alkaline complexes in igneous rocks. Nepheline is mostly found in the rock Nepheline Syenite in nature.
What type of rock is nepheline?
nepheline syenite, medium- to coarse-grained intrusive igneous rock, a member of the alkali-syenite group (see syenite) that consists largely of feldspar and nepheline. It is always considerably poorer in silica and richer in alkalies than granite.
Is nepheline a rock or mineral?
feldspathoid mineral
Nepheline is an important feldspathoid mineral. It is white, grey or yellow in colour with a vitreous lustre and a poor cleavage. The name Nepheline comes from the Greek word nephele, which means “cloud,” because it becomes strongly clouded when put in strong acid. Nepheline only forms in silica-poor rocks.
How can you tell nepheline from quartz?
Nepheline is softer than quartz and differs in optic sign. Nepheline occurs in alkali-rich, silicon poor igneous rocks (nepeline syenite, foidite and phonolite). May be found in some contact metamorphosed rocks.
Does nepheline have twinning?
Nepheline does not exhibit twinning and has low birefringence as evidenced by the gray interference color of the central crystal in this image.
What is the cleavage of nepheline?
Nepheline Mineral Data
| General Nepheline Information | |
|---|---|
| Chemical Formula: | (Na,K)AlSiO4 |
| Cleavage: | {1010} Poor |
| Color: | White, Gray, Brown, Brownish gray, Reddish white. |
| Density: | 2.55 – 2.65, Average = 2.59 |
Is nepheline a Pleochroic?
Nepheline does not exhibit twinning and has low birefringence as evidenced by the gray interference color of the central crystal in this image….Petrographic Data File.
| Nepheline | ||
|---|---|---|
| Property | Value | Comments |
| Color/Pleochroism | Colorless in thin section (non-pleochroic) | . |
What is nepheline syenite made of?
Nepheline syenite is a naturally occurring rock that consists mainly of the minerals albite, microcline and nepheline. This mineral raw material therefore contains no crystalline quartz; it is inert and is characterized in addition by a high degree of hardness (Mohs hardness 6.5).
What is the oldest type of syenite?
The oldest unit is fine-grained nepheline syenite, which is followed inward by massive and trachytoid khibinites (coarse-grained nepheline syenites), which make up most of the western parts of the intrusion.
What is the color of nepheline white?
Buerger M J , Klein G E , Hamburger G E , American Mineralogist , 32 (1947) p.197-197, The structure of nepheline White, Gray, Brown, Brownish gray, Reddish white.
What is the scale of the stubby hexagonal prism of nepheline?
Comments: Stubby, hexagonal prism of Nepheline in matrix. Location: Point of Rocks Mesa, Colfax County, New Mexico. Scale: Not Given. a = 10.01, c = 8.405, Z = 8; V = 729.35 Den (Calc)= 2.66