The Mineral CREEDITE

(under longwave UV light)

Chemistry: Ca3Al2SO4(F, OH)-2H2O , Hydrated Calcium Aluminum Sulfate Hydroxide Fluoride
Class: Sulfates

Uses: mineral specimens
Specimens

Creedite is a rather rare sulfate found as an accessory to highly oxidized ore bodies. It can be confused with cobalt-rich adamite when its color is purple. It lacks adamite's luster, though, and adamite's dome termination is not slanted, as creedite's is. Creedite's purple color is attractive and its crystal form is unique, making creedite a nice mineral collection addition.

PHYSICAL CHARACTERISTICS:

Color is white, colorless and purple.
Luster is vitreous.
Transparency crystals are transparent to translucent.
Crystal System is monoclinic; 2/m
Crystal Habits include prismatic crystals with a dome termination whose top edge is slanted with respect to length. Also acicular crystals in radiating groups.
Cleavage is perfect in one direction.
Fracture is uneven.
Hardness is 4.
Specific Gravity is approximately 2.7+ (average for translucent minerals)
Streak is white.
Associated Minerals are limonite, cassiterite, adamite and vanadanite.
Other Characteristics: color if present is unevenly distributed through the crystals.
Notable Occurrences include Mapimi, Mexico; Colquiri, Bolivia and Colorado, USA.
Best Field Indicators are crystal habit, associations and locality.