Haüyne [cubic, Na3Ca(Si3Al3)O12(SO3)], a member of the feldspathoid supergroup, is named after René Just Haüy, who is considered to be the father of mineralogy and crystallography. An old synonym ‘hauynite’ remains as a gemstone name. It occurs in alkali-rich volcanic rocks and in a few metamorphic rocks. It is a constituent mineral of lapis lazuli, as well as sodalite and lazurite, which are related minerals in the sodalite group. It usually occurs as aggregates of fine grained crystals and rarely as a transparent single crystal. It is known as a blue mineral, but can also be colorless, gray, yellow, green, and pink. Its earliest descriptions are from Vesuvius, Italy, which is a major locality of the mineral. The photograph by Koichi Momma (FOV: 19 mm) shows a blue crystal of haüyne on a specimen in the mineral collection of the National Museum of Nature and Science, NSM-MF14763.
(Explanation: Ritsuro MIYAWAKI)
