eudialyte

{{Infobox mineral | name = Eudialyte | category = Cyclosilicate | image = Eudialyte-163974.jpg | imagesize = 290px | caption = | formula = Na15Ca6(Fe,Mn)3Zr3SiO(O,OH,H2O)3(Si3O9)2(Si9O27)2(OH,Cl)2 | IMAsymbol = Eud | strunz = 9.CO.10 | system = Trigonal | class = Hexagonal scalenohedral (m) H-M symbol: ( 2/m) | symmetry = Rm | unit cell = a = 14.31, c = 30.15 [Å]; Z = 12 | color = Red, magenta, brown; also blue and yellow | habit = Crystals short rhombohedral to long prismatic, granular, irregular masses | twinning = | cleavage = Distinct on {0001} imperfect on {110} | fracture = Uneven | tenacity = Brittle | mohs = 5–6 | luster = Vitreous | refractive = nω = 1.606–1.610 nε = 1.610–1.613 | opticalprop = Uniaxial (+/−) | birefringence = δ = 0.004 | pleochroism = Weak: O= colorless, pale yellow, pink; E= pink to colorless | streak = White | gravity = 2.74–3.10 | melt = | fusibility = | diagnostic = | solubility = H2SO4 | diaphaneity = Transparent to translucent | other = Mildly 25px Radioactive | references = }} thumb|Pink eudialyte in syenite ([[lujavrite) from Poços de Caldas, Brazil. The white mineral is alkali feldspar, the black is aegirine, and the little brown bits are biotite.]]

Eudialyte, whose name derives from the Greek phrase , , meaning "well decomposable", is a somewhat rare, nine-member-ring cyclosilicate mineral, which forms in alkaline igneous rocks, such as nepheline syenites. Its name alludes to its ready solubility in acid.