haüyne

{{Infobox mineral | name = Haüyne | category = Tectosilicate minerals | group = Feldspathoid group, sodalite group | boxwidth = | boxbgcolor = | image = Hauyne-169903.jpg | imagesize = 260px | caption = Hauyne from Mayen, Eifel Mts, Rhineland-Palatinate, Germany | formula = | IMAsymbol = Hyn | molweight = 1,032.43 g/mol | strunz = 9.FB.10 (10 ed) 8/J.11-30 (8 ed) | dana = 76.2.3.3 | system = Isometric | class = Hextetrahedral (3m) H-M symbol ( 3m) | symmetry = P3n | unit cell = a = 9.08 – 9.13 Å; Z = 2 | color = Blue, white, gray, yellow, green, pink | habit = Dodecahedral or pseudo-octahedral | twinning = Common on {111} | cleavage = Distinct on {110} | fracture = Uneven to conchoidal | tenacity = Brittle | mohs = 5 to 6 | luster = Vitreous to greasy | refractive = n = 1.494 to 1.509 | opticalprop = Isotropic | birefringence = None, isotropic | pleochroism = None, isotropic | streak = Very pale blue to white | gravity = 2.4 to 2.5 | melt = | fusibility = 4.5 | diagnostic = | solubility = Gelatinises in acids | diaphaneity = Transparent to translucent | other = May fluoresce orange to pink under longwave ultraviolet light | references = }}

Hauyne or haüyne, also called hauynite or haüynite ( ), old name Azure spar, is a rare tectosilicate sulfate mineral with endmember formula . As much as 5 wt % may be present, and also and Cl. It is a feldspathoid and a member of the sodalite group. Hauyne was first described in 1807 from samples discovered in Vesuvian lavas in Monte Somma, Italy, and was named in 1807 by Brunn-Neergard for the French crystallographer René Just Haüy (1743–1822). It is sometimes used as a gemstone.