OGDENSBURGITE

Ca₂Fe³⁺₄(Zn,Mn)(AsO₄)₄(OH)₆.6H₂O 
Orthorhombic

Ogdensburgite was first described from Sterling Hill by Dunn (1981d) and was redefined on the basis of better quality material from Mapimi, Durango, Mexico, by Kampf and Dunn (1987).

Description

Sterling Hill ogdensburgite occurs as a thin dark orange-red to brown crust of platy crystals with the {001} perfect cleavage normal to the surface of the crusts. The dark color is the result of alteration; fresh material has a very bright reddish-orange color. The hardness is approximately 2, and the density is likely close to 3.11 g/cm³, rather than the value of 2.92 g/cm³ reported by Dunn (1981d). Optically, ogdensburgite is biaxial and negative; the indices of refraction are likely quite close to those reported by Kampf and Dunn (1987) for Mapimi material (a = 1.715, b = 1.783, and g = 1.785). X-ray methods are best for verification.

Composition

Ogdensburgite is a calcium zinc ferric-iron arsenate hydroxide hydrate mineral. A microprobe analysis by the writer is given in Table 25; the water content was shown to be 14.8 wt. % by Kampf and Dunn (1987), who also provided the formula noted above.

Occurrence and paragenesis

Ogdensburgite was found near the 340 level at Sterling Hill as crusts, botryoidal knobs, and protuberances coating low-grade black-willemite ore. It is associated with koettigite, adamite, yukonite, legrandite, pharmacosiderite, and other arsenates. It may have been locally abundant, but in the 1980’s many specimens of other minerals were sold mislabeled as ogdensburgite. 

Name

Ogdensburgite was named for the Borough of Ogdensburg, Sussex County, New Jersey, in which the Sterling Mine is located.

Copyright © 1995 by Pete J. Dunn			Website by Herb Yeates
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This page created: January 11, 2001