creedite

{{Infobox mineral | name = Creedite | category = Halide mineral | boxwidth = | boxbgcolor = | image = Creedite 3 photo fond.jpg | imagesize = 260px | caption = Creedite, Santa Eulalia District, Municipio de Aquiles Serdán, Chihuahua, Mexico | formula = Ca3Al2(SO4)(F,OH)10•2(H2O) | IMAsymbol=Cee | molweight = | strunz = 3.CG.15 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/c | unit cell = a = 13.91 Å, b = 8.58 Å, c = 10 Å; β = 94.4°; Z = 4 | color = Colorless, white, violet, orange | habit = Generally appears as anhedral to subhedral in matrix; bladelike prismatic and radial, drusy to granular aggregates | cleavage = Perfect on {100} | mohs = 3.5 - 4 | luster = Vitreous | streak = White | density = | fracture = Conchoidal | tenacity = Brittle | opticalprop = Biaxial (-) | refractive = nα = 1.461 nβ = 1.478 nγ = 1.485 | birefringence = δ = 0.024 | dispersion = r > v strong | pleochroism = | 2V = 65° | fluorescence= | absorption = | gravity = 2.71 | fusibility = | diagnostic = | diaphaneity = Transparent to translucent | other = | references = }}

Creedite is a calcium aluminium sulfate fluoro hydroxide mineral with formula: Ca3Al2SO4(F,OH)10·2(H2O). Creedite forms colorless to white to purple monoclinic prismatic crystals. It often occurs as acicular radiating sprays of fine prisms. It is translucent to transparent with indices of refraction of nα = 1.461 nβ = 1.478 nγ = 1.485. It has a Mohs hardness of 3.5 to 4 and a specific gravity of 2.7.