Sodalite

Sodalite is a blue tectosilicate mineral.
It is named after the sodium content.
In mineralogy it may be classed as a feldspathoid.
It is used in jewelry.
It looks similar to lazurite and lapis lazuli but sodalite rarely contains pyrite and distinguished by its white streak.
Sometimes it is referred as "poor man's lapis".
Ideally sodalite has Na4Cl and sodalite is Co2 - free.

Sodalite from Bolivia and Brazilia

The brown-red crystals are Andradite

Properties:
Category: Tectosilicates without zeolitic
Formula: Na8(Al6Si6O24)Cl2 - Sodium aluminum silicate with chlorine and occasionally sulfur
Sodium 18,98%; aluminum 16,70%; silicon 17,39%; chlorine 7,32%; oxygen 39,62%
Na2O 25,58%; Al2O3 31,56%; SiO2 37,20%; Cl 7,32%
Crystal system: cubic
Color blue, green, yellow, violet and veining is common
Is often opaque but can be transparent to translucent
Fracture: Conchoidal to uneven
Hardness: 5,5-6 Mohs
Density: 2,29
Luster dull vitreous to greasy
Streak white
Specific gravity 2,27-2,33
Formed in nepheline syenites, phonolites and related rock types; in metasomatized calcareous rocks, in cavities in ejected volcanic blocks.
Common impurities: Fe, Mn, K, Ca, H2O, O, S, Br
Optical properties: isotropic
Special properties: fluorescence bright red-orange
cathodoluminescence and fluorescence under long and short UV with yellowish phosphorescence
may be photochromic
tenebrescence / photochromatism / photochromism presented in a variety of sodalite named hackmanite
Soluble in hydrochloric acid and nitric acid

Tests:
fluorescence with creamy-white, yellow or orange in shortwave UV and pink, white, red in longwave UV.
Hackmanite fluoresces orange to red in shortwave and orange in longwave UV.
Hardness 5,5-6 Mohs and streak white
May give off odor of H2S on fracture.

Luminescence:
Most sodalite will fluoresce orange under UV and hackmanite exhibits tenebrescence.
Short UV yellow white orange; intensity medium
Long UV yellow white, red orange; intensity very strong and frequency often
Other colors in long wave: white, yellow, red, pink strong, pink pale
Other colors in shortwave: orange, pink strong, pink pale, cream, green
Phosphorescence: in long wave: blue white with strong intensity and frequency often
In short wave color bluish white, intensity very strong, frequency often
Has tenebrescence, changing color from white pale to purple, violet or pink in natural light and accelerated in UV light
Has Thermoluminescence
Hackmanite is strongly tenebrescent
Main activator: Sulfur
Other activators: UO2 (Uranyl ion) as impurities; Fe; Mn
S: 587, 628, 653, 677, 707, 732 nm
Fe: 687-720 nm
UO2: 495, 515, 537 nm
Mn replacing Na: 650 nm
Ping and orange fluorescence of a sodalite sample under UV longwave

Distinguishing similar minerals:
Lazurite - has a blue streak and usually associated with pyrite.
Lazulite - lacks white veins and is not fluorescent.
Azurite - softer nad has a blue streak.

Hackmanite is a variety of sodalite with tenebrescence.
Has a very pale-white violet.
Some hackmanite can start with a creamy white and develops a violet pink-red color in sunlight.
When left in dark, the violet will fade again. Tenebrescence can be accelerated with longwave or shortwave ultraviolet light.

Sodalite occurs in vein in igneous rock and in association with leucite, cancrinite and natrolite.
Can be associated with nepheline, titanian andradite, aegirine, microcline, sanidine, albite, calcite, fluorite, ankerite and baryte.

Sources: https://www.mindat.org/min-3701.html
http://webmineral.com/data/Sodalite.shtml#.Xa1_zugzZrS
https://www.minerals.net/mineral/sodalite.aspx
http://www.fluomin.org/uk/fiche.php?id=662&name=SODALITE

Other names: sodalit sodalite sodalitul