Nepheline Syenite


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nepheline syenite

[′nef·ə‚lēn ′sī·ə‚nīt]
(petrology)
A phaneritic plutonic rock with granular texture, composed largely of alkali feldspar, nepheline, and dark-colored materials.

Nepheline Syenite

 

a magmatic alkali rock composed of nepheline, alkali feldspars (sanidine, orthoclase, or microcline), biotite, and alkali amphiboles and pyroxenes. It also contains zirconium-bearing silicates (zircon, eudialyte) and titanium-bearing silicates (sphene, lamprophyllite), as well as minerals containing F, P2O5, CO2 (cancrinite, calcite, apatite, fluorite) and rare earths (rinkolite, loparite). Nepheline syenite contains 50–56 percent SiO2, 19–24 percent Al2O3, a small quantity of Ca and Mg, and 15–17 percent K and Na.

There are numerous varieties of nepheline syenites, including (1) chibinites, greenish gray coarse-grained pyroxene nepheline syenites, with pegmatic texture; (2) rischorites, yellowish gray or greenish gray rocks with poikilitic texture; (3) lujauvrites, greenish black rocks with marked trachytic texture; (4) miascites, micaceous lamellar nepheline syenites found in the Urals; (5) mariupolites, distinctive albite-rich nepheline syenites; and (6) saibarites, melanocratic nepheline syenites found in Siberia and elsewhere. In addition to the USSR, nepheline-syenite deposits are also found in the vicinity of Oslo, Norway, and in southern Greenland, in Canada, in southern Africa, and on Madagascar. Nepheline syenites occur in association with apatites (Kola Peninsula), graphite (Saian Mountains), cryolite (Greenland), and a number of rare elements.

REFERENCES

Kupletskii, B. M. Formatsiia nefelinovykh sienitov SSSR. Moscow-Leningrad, 1937.
Kupletskii, B. M. “K voprosu o kolichestvenno-mineralo-gicheskom sostave fel’dshpatoidnykh porod.” Dokl. AN SSSR: Novaia seriia, 1946, vol. 52, no. 3.
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was approached with a new sort of freeness; a little Gerstley Borate here and a little Nepheline Syenite there gave me the sheen and shine that 1 was looking for.
Other extender pigments noted in commercial products include Nepheline Syenite, Kaolin, calcium carbonate, and, while not a traditional coating extender, ground tire rubber.
The studied rocks were concentrated biotite ("biotite") (Mogi das Cruzes, Sao Paulo State), nepheline syenite ("syenite") (Pocos de Caldas plateau, Minas Gerais State), and green banded argillite ("argillite") (Cedro de Abaete region, Minas Gerais State).
The host rock to these minerals, a coarse-grained nepheline syenite (Fig.
the country rock) in close proximity to the intrusions has been fenitized to varying degrees, producing quartz syenite, alkali syenite, nepheline syenite, pyroxene nephelinite, microcline syenite and albite syenite.
The chief metallic mineral resources include: gold, zinc, copper and tin-tungsten, while the chief non-metallic resources include: phosphate, high-grade silica sand, feldspar and nepheline syenite, kaolin, basalt and scoria, gypsum and anhydrite, limestone and dolomite, ornamental stone and quartz.
The Khibiny Massif is a famous and unique mineral locality that is composed of a nepheline syenite intrusion rich in a large number of rare minerals.
Among the additives options that prevent thin plastic layers from sticking to each other, 'Talc, nepheline syenite, and DE have been the incumbent high-performance antiblock minerals in plastic films," says John Flurley, president and CEO of Trinity Resources.
distributor is Maroon Group, Avon, Ohio) is said to combine the best attributes of talc, nepheline syenite (NS), and diatomaceous earth (DE).
Other resources are Nepheline Syenite, phosphates, gemstones, and metallic minerals including gold and base metals and variety of other industrial minerals.