What is Haüyne?
Haüyne is a vivid blue feldspathoid mineral found mainly in silica-undersaturated volcanic rocks and prized by collectors for its saturated colour.
Mineralogy and structure
Reference formula: Na3Ca(Si3Al3)O12SO4. Haüyne has a cubic feldspathoid framework with sulfate and other anions in its cavities. Its colour can vary with sulfur, chlorine and oxidation state, so a blue grain is not identified by colour alone. Haüyne belongs to the silicates and has a cubic crystal system. Typical hardness is 5.5–6 on the Mohs scale and specific gravity is approximately 2.4–2.5.
Colour and appearance
Typical colours include blue, blue-green, grey, white. The usual dodecahedral, granular, massive habit and vitreous lustre are useful descriptive features, but colour alone is not diagnostic.
Formation and localities
Haüyne forms in or is associated with alkaline volcanic rocks, nepheline syenites and silica-undersaturated lavas. Important documented localities include Afghanistan, Germany, Italy, Russia, Canada and the United States.
Collecting and care
Protect transparent grains and crystal edges from impact; preserve the volcanic host and locality documentation.
