STERLINGHILLITE

Mn₃(AsO₄)₂.4H₂O?                                  Symmetry unknown

	Figure 25-41. Curved arrays of platy sterlinghillite crystals from Sterling Hill. Field of view is 0.04 mm in maximum dimension.

Sterlinghillite was described from Sterling Hill by Dunn (1981a); it has not been found at Franklin. It is an incompletely described species with indefinite formula, which was published prematurely when the author’s enthusiasm overcame his judgment. It remains, however, a valid species. A second specimen of the original assemblage was described by Cianciulli (1995b).

Description

Sterlinghillite occurs in two habits on the type specimen: as soft pearly microscopic crystals which resemble laumontite and as 0.1 mm spherulitic clusters of platy crystals (Figures 25-41 and 25-42).

	Figure 25-42. Platy rectangular sterlinghillite crystals in a vug from Sterling Hill. Field of view is 0.04 mm in maximum dimension.

Sterlinghillite is white to very light pink with one cleavage parallel to the elongation direction. The luster is silky on external crystal faces. The density is 2.95 g/cm³, as measured, but may be low due to the porosity of the aggregate. There is no discernible fluorescence in ultraviolet. It is best verified using X-ray methods.

Composition

Sterlinghillite is a manganese arsenate hydrate mineral. A microprobe analysis is given in Table 25.

Occurrence and paragenesis

Sterlinghillite occurs as 0.1 mm clusters on fracture surfaces in franklinite/sphalerite  ore, which is in contact with loellingite and calcite.

Name

Sterlinghillite was named for Sterling Hill in the Borough of Ogdensburg.

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