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Hackmanite  (variety of Sodalite)
Current inventory:  0 gems
 

Chemistry:  Na₈Al₆Si₆O₂₄(Cl₂,S)

Discovered in 1811;   IMA status: Hackamnite, Not Valid; Sodalite, Valid
Hackmanite is named for Finnish geologist, Victor Hackman (1866-1941). 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

Related to:

Sodalite Group

Crystal Data

Crystallography:

Isometric - Hextetrahedral

Crystal Habit:

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

Twinning:

On [111], common, forming pseudohexagonal prisms by elongation along [111].

Physical Properties

Cleavage:

[110] Poor

Fracture:

Uneven to Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

5.5 - 6.0

Density:

2.14 - 2.40 (g/cm³)

Luminescence:

Bright red-orange cathodoluminescence and fluorescence under LW and SW UV, with yellowish phosphorescence; may be photochromic in magentas.

Radioactivity:

Not Radioactive

other:

May give of the odor of H₂S on fracture.

Optical Properties

Color:

Colorless, White, Gray, Pink to Violet, Lavender, Purple, pale Blue

Transparency:

Transparent to Translucent

Luster:

Vitreous, Greasy

Refractive Index:

1.483 - 1.487  Isotropic

Birefringence:

0.000  Isotropic minerals have no birefringence

Dispersion:

Weak; 0.018

Pleochroism:

None

Occurances

Geological Setting:

Formed in nepheline syenites, phonolites, and related rock types. In metasomatized calcareous rocks, and in cavities in ejected volcanic blocks.

Common Associations:

Nepheline, Cancrinite, Titanian Andradite, Aegirine, Microcline, Sanidine, Albite, Calcite, Fluorite, Ankerite, Barite.

Type Locality:

Tawa valley, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia.

Year Discovered:

1811

View mineral photos:

Hackmanite Mineral Photos and Locations

More Information

Mindat.org (Hackmanite)
Mindat.org (Sodalite)
Webmineral.com (Sodalite)

Hackmanite is an important variety of Sodalite and is a member of the Sodalite group that also includes Haüyne, Tugtupite and Lazurite. Sodalite is also a member of the Feldspathoid group of minerals that includes Cancrinite, Lazurite, Leucite, and Nepheline. Hackmanite exhibits Tenebrescence. This means it may turn shades of pink, violet or purple when exposed to sunlight or shortwave (SW) UV light and when removed from the light it gradually fades back to white or pale yellow. This process is accelerated by the use of shortwave UV light and the cycle is repeatable.

There are many sources of Sodalite, but very few for gem quality crystals of Hackmanite. Some of these are Koksha Valley, Badakhshan Province, Afghanistan; Poudrette quarry, Mont Saint-Hilaire, Rouville County, Québec, Canada; Svintsovyi Ruchei (Lead Creek), Kukisvumchorr Mt, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia
 

  
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