Creedite: Gemstones Information
Creedite is Ca3Al2 (SO4)(F,OH)102H2O and forms monoclinic crystals of prismatic habit or radiating masses. Some light purple transparent stones have been cut. The hardness is 3.5 and there is a perfect cleavage. The RIs are 1.461, 1.478, 1.485, biaxial negative and the SG is 2.71. Facetable material has been found at a fluorite/barite mine at Santa Eulalia,Chihuahua, Mexico. Creedite is a rare mineral, occurring in fluorite-rich hydrothermal mineral deposits.