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Blocky Nepheline Crystals

The Mineral nepheline




Nepheline is a rock-forming mineral. It is usually massive and in unattractive specimens, though a handful of localities have produced well-crystallized examples of this mineral. Nepeheline is a primary constituent of nepheline syenite rocks and nepheline syenite pegmatites, forming in alkali-rich plutonic environments often together with a host of rare minerals.
Chemical Formula (Na,K)AlSiO4
Composition Sodium potassium aluminum silicate
Color Colorless, white, gray, cream, yellow, brown
Streak White
Hardness 5.5 - 6
Crystal System Hexagonal
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
Crystals, which are uncommon, are prismatic, stout or tabular, and usually have a good hexagonal shape with a flattened termination. Crystals are often intergrown or stacked. Nepheline is most often massive or grainy.
Transparency Transparent to opaque
Specific Gravity 2.5 - 2.6
Luster Vitreous to greasy
Cleavage 2,3
Fracture Subconchoidal to uneven
Tenacity Brittle
Complex Tests Becomes cloudy when dipped in acid
In Group Silicates; Tectosilicates; Feldspathoid Group
Striking Features Environment, greasy luster, and cleavage
Environment In alkaline igneous nepheline syenites and nepheline syenite pegmatites.
Rock Type Igneous
Popularity (1-4) 3
Prevalence (1-3) 2
Demand (1-3) 3


Nepheline AUCTIONS
OTHER NAMES
Elaeolite Obsolete synonym of Nepheline.



USES
Nepheline is used in the production of glass and ceramics.

NOTEWORTHY LOCALITIES
Though massive Nepheline can be found in many locations, good examples of this mineral are only found in a handful of places. Nepheline with a brilliant blue coating of Nosean-impregnated Sodalite comes from Sar-e-Sang, Kochka Valley, Badakshan Province, Afghanistan. Some of the best crystals of Nepheline, in white and gray prismatic crystal clusters, are found in Bou Agrao Mt., Khénifra Province, Morocco. Excellent white and colorless crystals were found in Italy at Monte Somma, Vesuvius; and in several areas around Rome area. Microscopic colorless Nepheline crystals come from Üdersdorf, Hillesheim, and Ettrigen, in the Eifel Mountains of Germany.

In Canada, large, well-formed Nepheline crystals occur in Hastings Co., Ontario, in both Bancroft and at Dungannon Township (at Davis Hill). Small gray crystals came from Mont Saint Hilaire, Quebec. In the U.S., rough Nepheline masses come from Litchfield, Kennebec Co., Maine; and small crystals were found in Magnet Cove, Hot Spring County, Arkansas.

COMMON MINERAL ASSOCIATIONS
Albite, Apatite, Calcite, Biotite, Sodalite, Hematite, Aegirine, Cancrinite, Sodalite

DISTINGUISHING SIMILAR MINERALS
Feldspars - Lack greasy luster and have better cleavage.
Scapolite - Different cleavage.


nepheline PHOTOS
 
ADDITIONAL RESOURCES
 
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