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Sodalite
Current inventory:  0 gems
 

Chemistry:  Na₈Al₆Si₆O₂₄Cl₂

Discovered in 1811 ;   IMA status: Valid (pre-IMA; Grandfathered).
Sodalite is named after its chemical composition containing Sodium (Na).

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/J.11-10

Nickel-Strunz 10th Ed. ID:

9.AC.05

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H₂O
B : Tektosilicates with additional anions
(Sodalite group)

Crystal Data

Crystallography:

Isometric - Hextetrahedral

Crystal Habit:

Crystals rare, typically dodecahedra, to 10 cm; as embedded grains or massive.

Twinning:

Common, forming pseudohexagonal prisms.

Physical Properties

Cleavage:

[110] Poor

Fracture:

Conchoidal to Uneven, Irregular

Tenacity:

Brittle

Hardness (Mohs):

5.5 - 6.0

Density:

2.27 - 2.33 (g/cm³)

Luminescence:

Bright red-orange under SW and LW UV. cathodeluminescent. Yellowish phosphorescence, may be photochromic in magentas.

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White, Yellowish, Greenish, Gray, light to dark Blue, Azure Blue, Pink

Transparency:

Transparent to Translucent

Luster:

Vitreous, Greasy

Refractive Index:

1.483 - 1.487  Isotropic

Birefringence:

0.00 (Isotropic)

Dispersion:

0.018

Pleochroism:

None

Occurances

Geological Setting:

Found in nepheline syenites, phonolites, volcanic ejecta, metasomatized calcareous rocks.

Type Locality:

Ilimaussaq complex, Narsaq, Kitaa (West Greenland) Province, Greenland

Year Discovered:

1811

View mineral photos:

Sodolite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Sodalite is a member of the Sodalite mineral group that also includes Hackmanite, Tugtupite and Lazurite. The Sodalite mineral group is named after its most common member. Sodalite is also one of the members of the Feldspathoid group of minerals that includes Cancrinite, Haüyne, Lazurite, Leucite, Nepheline and Sodalite. Minerals with chemistries that are close to those of the alkalai Feldspars, but are poor in silica (SiO2) content, are called Feldspathoids. Sodalite is mostly known for vivid blue, opaque material that is seldom transparent and clean enough for faceting. Faceted gems are very rare and usually very small.

Although Sodalite is found in several localities around the world, few of these produce transparent crystals for faceting. A recent find in Afghanistan has produced some beautiful, colorless, very clean gems. Other locations such as Bancroft, Ontario, Canada are the source of small, semi-transparent, vivid blue gems.
 

  
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