Ogdensburgite

ogdensburgite

parasymplesite

kottigite

villyaellenite

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Formula: Ca₂Fe³⁺₄Zn(AsO₄)₄(OH)₆.6H₂O
Hydrated arsenate containing hydroxyl
Crystal System: Orthorhombic
Specific gravity: 3.11 measured, 3.39 calculated
Hardness: 2
Streak: Light brownish red
Colour: Reddish brown to brownish red
Luminescence: Not fluorescent under UV
Environments

Hydrothermal environments

Ogdensburgite was first described from Sterling Hill in 1981 and was redefined on the basis of better quality material from Mapimi in 1987. Localities

At the Ojuela Mine, Mapimí, Mapimí Municipality, Durango, Mexico, the second occurrence of ogdensburgite has yielded material superior to that found at the type locality, the Sterling Hill mine. At Mapimi, ogdensburgite occurs as dark brownish-red intergrown blades up to 1 mm in length, associated with arseniosiderite, adamite, chalcophanite and villyaellenite.
The measured specific gravity is 3.11 which differs significantly from that determined from type material, and led to a new ideal formula with calculated specific gravity of 3.39; site vacancies may account for the much lower observed specific gravity (AM 72.409-412).

At the type locality, the Sterling mine, Sterling Hill, Ogdensburg, Franklin Mining District, Sussex County, New Jersey, USA, ogdensburgite was found as somewhat earthy looking thin coatings usually on willemite-franklinite and as encrustations of minute plates and coatings along fractures in calcite. The crusts are less than 0.1 mm thick and resemble dark red velvet. Associated minerals include parasymplesite and köttigite (Mindat).

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