Mineral
Creedita
Ca₃Al₂(SO₄)(F,OH)(SO₄)₃·2H₂O · Sulfatos
Creedite is a rare hydrated complex calcium–aluminium fluorosulphate that forms in oxidation zones of complex sulphide deposits.
It commonly occurs with fluorite, whose partial dissolution supplies the fluorine required for crystallisation. Acidic fluids dissolve the pre-existing fluorite and creedite recrystallises in complex forms. In such alteration cavities it may grow as spherical aggregates. When spheres develop within clay pockets, terminations form in all directions without striking a hard substrate.
Many crystals appear to grow suspended in clay, with no visible point of attachment. This growth accounts for complete sphere-like aggregates. Crystallised creedite specimens were extremely rare until the discovery at Mina Navidad, Mapimí. Even then, complete spheres with a floating aspect remained highly sought after; with the mine now closed, even more.
Etymology
From English "Creede", the original description locality (Colorado, USA), with the mineral suffix "-ite".