HYDROHETAEROLITE

Zn₂Mn³⁺₄O₈.H₂O
Tetragonal

Hydrohetaerolite, a zinc manganese oxide hydrate mineral, was first described from Sterling Hill by Palache (1928a, 1935), and it was restudied by Frondel and Heinrich (1942); their conclusions were discussed by Ramdohr and Frenzel (1956). It has not been reported from Franklin. The very first discovery of its uniqueness was by Moore (1877), who called it zinc hausmannite, but he failed to establish that his definition of it was correct. The history of this mineral is a confused one, as set out in the above-cited papers. The mineral was redefined by Wadsley (1955) using material of uncertain provenance and by McAndrew (1956) using material from Colorado. The description here is drawn from Palache (1935); the writer has not studied this mineral.

Description

Hydrohetaerolite occurs in massive form, as bulbous, botryoidal, or mammillary masses, and is dark brown, nearly black, with a submetallic luster. A fibrous texture is apparent. The hardness is approximately 5, and the observed density varies from 4.85 to 4.93 g/cm³. No new analytical data have been obtained; the extant data are given by Palache (1935).

Occurrence and paragenesis

Hydrohetaerolite occured in the Passaic Mine at Sterling Hill, mined extensively for hemimorphite in the 1870’s and, together with the Noble Mine, the source of many secondary manganese oxides such as chalcophanite, hetaerolite, birnessite, cryptomelane, and others. Hydrohetaerolite occurs intimately associated with chalcophanite, and Moore (1877) argued for its formation as a result of the progressive alteration of franklinite; this proposal was supported by Palache (1935), but ignored by other investigators, and the assemblage has not been restudied.

Name

Hydrohetaerolite was named in recognition of its close relation to hetaerolite and its water content.

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