Nepheline Value, Price, and Jewelry Information

By Andrew Silver, USGS.Materialscientist at en.wikipedia [Public domain or Public domain], from Wikimedia Commons

Nepheline

A variety called elaeolite is red, green, brown, or gray, massive or in crystals filled with minute inclusions. These inclusions produce a sheen that yields a catseye effect in cabochons. Facetable nepheline is a great rarity, and very few gems have been cut, always in the 1-2 carat range or smaller.

Nepheline Information

Data Value
Name Nepheline
Varieties Elaeolite
Colors Colorless, white, gray, yellowish, greenish, bluish, dark green, brick red, brownish red.
Scientific Name Nepheline
Crystallography Hexagonal. Crystals stumpy, sometimes very large; massive, compact; in grains.
Refractive Index 1.526-1.546
Luster Vitreous to greasy.
Hardness 5.5-6
Fracture Subconchoidal
Specific Gravity 2.55-2.66
Birefringence 0.004
Cleavage Indistinct
Dispersion Low.
Stone Sizes Cabochons of nepheline have been cut in various sizes; crystals, especially those from Canada, can reach enormous size but are not attractive. Faceting material is extremely rare and very small.
Luminescence Medium light blue (Germany) or medium dull orange (Ontario) in LW.
Luminescence Present Yes
Luminescence Type Fluorescent, UV-Long
Transparency Transparent to opaque.
Absorption Spectrum Not diagnostic.
Phenomena Chatoyancy.
Formula

(Na,K)AlSiO4.

Optics

o = 1.529-1.546; = 1.526-1.542. Uniaxial (-).

Optic Sign Uniaxial -

Optics: o = 1.529-1.546; e= 1.526-1.542.

Uniaxial (-).

Occurrence: Plutonic and volcanic rocks; pegmatites associated with nepheline syenites.

Julienhaab district, Greenland; Langesundsfford, Norway;

China; Germany; Finland; Russia; Myanmar; North Korea; South Korea.

Various localities in the United States, especially Maine and Arkansas.

Ontario, Canada: crystals up to 15 inches long (non-gemmy).

Vesuvius, Italy: small, glassy transparent grains.

Comments: A variety called elaeolite is red, green, brown, or gray, massive or in crystals filled with minute inclusions. These inclusions produce a sheen that yields a catseye effect in cabochons. Facetable nepheline is a great rarity, and very few gems have been cut, always in the 1-2 carat range or smaller.

Name: From a Latin word meaning cloud because it becomes cloudy when immersed in acid. Elaeolite is from a Latin Word for oil because of its greasy luster.