Hauyne

Hauyne forms a solid solution series with Lazurite, essentially sharing the same chemical formula, but with a variation of sulfide over sulfate. Hauyne has the sulfate radical dominating, whereas Lazurite has the sulfide element dominating. Much of the known Lazurite specimens are actually sulfate-dominating, which means they are in fact Hauyne and not Lazurite. This is especially true at the most famous locality for Lazurite at Sar-e-Sang in the Kokcha Valley of Afghanistan, where the material labelled as Lazurite has been determined to really be Hauyne. Despite this, the mineral community still generally accepts this material as Lazurite notwithstanding the scientific inaccuracy. It is generally accepted to refer to the opaque, non-fluorescent, ultramarine-blue material as Lazurite, whereas Hauyne describes the transparent to translucent material.

Hauyne was named in 1807 in honor of French mineralogist and crystallographer Abbé Rene Just Haüy (1743-1822), curator of the Muséum National d'Histoire Naturelle in Paris.

Perhaps the most well-known locality for Hauyne is the Eifel Mountains of Germany, especially at the In den Dellen quarries, in Niedermendig. The locality has produced exceptional neon-blue crystals in a pumice matrix, though they are usually crudely formed.

The classic locality of Monte Somma, Vesuvius, Italy has also produced Hauyne with exceptional blue color, although usually in very small crystals. Large, bluish-white crystals have come from the Alban Hills and Sacrofano, in Rome Province, Latium, Italy. Large Hauyne crystals intergrown with white Gonnardite, and sometimes with a greenish tinge, are found in Sar-e Sang, Kokcha Valley, Badakshan Province, Afghanistan.