Gormanite

gormanite

souzalite

arrojadite

ludlamite

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Formula: Fe2+3Al4(PO4)4(OH)6.2H2O
Hydrated phosphate containing hydroxyl, forms a series with souzalite
Specific gravity: 3.13
Hardness: 4 to 5
Streak: Pale green
Colour: Blue green to dark green
Environments

Plutonic igneous environments
Pegmatites

Gormanite forms as a late stage mineralisation in granite pegmatites (Mindat).

Localities

There are two co-type localities, Big Fish River, and Rapid Creek, both in the Dawson mining district, Yukon, Canada. Gormanite-souzalite crystals are very common here, seen in thin sections of the phosphatic ironstone beds as green, elongate crystals in radial aggregates, and in open fractures as elongate, blade-like crystals. In many fractures gormanite-souzalite crystals constitute the only phosphate mineral and are generally accompanied by quartz and siderite. Elsewhere, gormanite-souzalite has been found in close association with ludlamite, arrojadite, kryzhanovskite and oxidised vivianite. In places, needles of gormanite-souzalite are included in quartz, giving the quartz crystals a green color. The absence of any sign of metamorphism in the surrounding rocks indicates that these have crystallised at a low temperature (CM 19.381-387).

At Bisbee, Cochise County, Arizona, USA, gormanite occurs in fractures in tonalite with chlorite, calcite and quartz (HOM).

At the Chickering Mine, Walpole, Cheshire county, New Hampshire, USA, gormanite is rare in the pegmatite deposit. Two known occurrences of several specimens each have been collected. One comprises blue-green, partially embedded, fibrous masses in siderite, the other medium to dark green lamellar sheaves over an aqua core. These sheaves occur in very small primary phosphate dissolution cavities in a medium grained siderite matrix. Siderite and embedded childrenite are the only associated minerals noted (R&M 90.5.417).

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