Creedite, Navidad Mine, Rodeo, Durango, Mexico. Size is about 10 × 10 × 7 cm. — Photo: JJ Harrison ( https://www.jjharrison.com.au/ ) · CC BY-SA 3.0
Creedite
A calcium-aluminium sulfate-fluoride forming colorless-to-purple radiating sprays of monoclinic prisms.
Intro adapted from Wikipedia (CC BY-SA).
Creedite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Ca₃Al₂(SO₄)(OH)₂F₈·2H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: Mohs hardness 4; specific gravity 2.71–2.73; Vitreous luster; refractive index 1.475; optically biaxial.
IMA symbol Cee, grandfathered status — known before the IMA’s founding, named in 1916.
Uncommon in fluorite-rich hydrothermal mineral deposits.
It is found associated with Fluorite, barite, kaolinite (Wagon Wheel Gap, Colorado, USA).
The name refers to the occurrence near Creede, Colorado, USA.