What is Ussingite?
Ussingite is a rare sodium aluminium silicate found in strongly alkaline nepheline-syenite environments, usually as pale massive or granular material.
Mineralogy and structure
Reference formula: Na2AlSi3O8(OH). Ussingite is triclinic and occurs in unusual silica-undersaturated alkaline systems, commonly with sodalite, steenstrupine and aegirine. The exact COD 9000390 model supports the structure page. Ussingite is classified with silicates and has triclinic crystal symmetry. Typical hardness is 5.5–6 on the Mohs scale and specific gravity is approximately 2.4–2.5.
Colour, lustre and habit
Typical colours include white, colourless, pale pink, lavender, grey. The usual massive, granular, tabular habit and pearly, vitreous, greasy lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Ussingite forms in or is associated with nepheline-syenite complexes, alkaline pegmatites and late-stage cavities rich in sodium-bearing fluids. Important documented localities include Greenland, Russia, Canada, Norway and the United States.
Pale colour from an extreme alkaline rock
Ussingite is a quiet-looking mineral with an unusual geological message: its presence points to sodium-rich, silica-undersaturated fluids in an alkaline igneous complex.
Collecting and care
Protect from acids and scratches; clean gently with a soft cloth and preserve the alkaline host-rock association.
