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Formula: Ca3Al2(SO4)(OH)2F8.2H2O
Compound halide
Crystal System: Monoclinic
Specific gravity: 2.713 to 2.73 measured, 2.715 calculated
Hardness: 4
Streak: White
Colour: White, violet, colourless; colourless in transmitted light
Solubility: Slowly soluble in acids
Environments
Creedite is an uncommon halide in fluorite-rich hydrothermal
mineral deposits
(HOM).
Localities
At the Akchatau Mine, Akchatau, Shet, Karaganda Region, Kazakhstan, creedite occurs with
quartz
(FM 81648).
Creedite from Akchatau - Image
The Navidad Mine, Indé Municipality, Durango, Mexico, exploits four vuggy
fluorite-quartz veins, the
largest of which is 4 to 5 meters wide, and is the source of the abundant creedite that is found as an
alteration product of the fluorite. The main vein is heavily
brecciated by tectonic movement that followed the
fluorite emplacement, and the creedite then grew within earthy
iron oxides and clays that filled the
breccia voids.
The lustrous crystals range from colourless to, rarely, pale purple and transparent, but most specimens are
combinations of colourless and shades of yellow to orange and reddish orange. The orange colour is not surface
staining, but instead forms colour zones within the crystals. Coarse black inclusions of
cryptomelane and
cryptomelane-stained creedite are common. Broken fragments of
fluorite are commonly overgrown by or included in creedite
crystals, adding green or violet accents. Creedite crystals also occur on massive, fine-grained, sparkly
white creedite matrix. In most specimens, creedite forms clusters and radiating, spherical
aggregates of sharp, lustrous crystals to 1.5 cm or so, arranged in spiky groups up to 18 cm across; still larger
specimens have been recovered showing two or three of the spheres clinging together. On a few rare specimens the
creedite clusters rest on intensely green crystalline fluorite.
In late 2019, radiating clusters of pale to medium pink to lavender creedite crystals up to 1 cm long were
found on green and purplish fluorite and also on an unidentified black
matrix, possibly manganese-rich
(Minrec 55.6.862).
Creedite from the Navidad Mine - Image
At the Cresson open pit, Eclipse Gulch, Cripple Creek Mining District, Teller county, Colorado, USA, creedite
has
been found associated with celestine,
gearksutite, pyrite and
rhodochrosite. Gearksutite
is generally the last of the minerals to form. Some specimens show celestine
intergrown with or overlying creedite
(Minrec 36.2.168).
Creedite from the Cresson Open Pit -
Image
At the the type locality, the Colorado Fluorspar Company Mine, Wagon Wheel Gap, Mineral county, Colorado, USA,
creedite occurs in the upper portions of a fluorite -
baryte vein, associated with fluorite,
halloysite, baryte and
kaolinite
(AM 17.75-77, AM 37.787-790).
The host rock for the fluorite veins is Miocene-aged
tuff, tuff
breccia, and intermediate to silicic lava flows. Creedite was
found
in the widest portions of the veins where cavities in the massive fluorite
existed.
Other minerals found in these deposits were baryte,
calcite, covellite,
gearksutite, pyrite and
quartz. The fluorite mineralisation
probably originated with hot spring fluids, which precipitated fluorite and
associated minerals at low confining pressures, ie at shallow depths
(R&M 93.4.369-372).
Creedite from Wagon Wheel Gap -
Image
At the small gold camp of Granite (now abandoned), Tonopah Mining District,
San Antonio Mountains, Nye county, Nevada, USA,
some specimens of the ore found in the small veins of the district in the oxidised zone contain creedite needles
to 2mm, associated with fluorite and
halloysite. The gold-bearing deposits
here are apparently fluorite-quartz
veins with free gold. The creedite probably results from the action of
aluminium bearing solutions on fluorite. The
gold of the veins is primarily inclosed in
fluorite but some crystals of creedite were found with enclosed plates of
gold, suggesting that the fluorite was
removed and its place taken by creedite
(AM 17.75-77, AM 37.787-790).
Creedite from the San Antonio Mountains -
Image
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