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Blocky Nepheline Crystals
SILICATES; TECTOSILICATES; FELDSPATHOID GROUP · HEXAGONAL

Nepheline

(Na,K)AlSiO4

Hardness
5.5–6
Streak
White
Spec. Gravity
2.5–2.6
System
Hexagonal

About

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.

Crystal Forms & 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.

Complex Tests

Becomes cloudy when dipped in acid

Striking Features

Environment

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

Distinguishing Similar Minerals

Photos

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Crystal forms

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Hexagonal