Willet Mine - Lardeau British Columbia, Canada — Photo: Pacific Museum of Earth from Canada · CC BY-SA 2.0
Woodruffite
Woodruffite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Zn₂(Mn⁴⁺,Mn³⁺)₅O₁₀·4H₂O.
It crystallizes in the monoclinic crystal system.
Key properties: Mohs hardness 4.5; specific gravity 3.71–4.01; Brown streak; Dull luster.
IMA symbol Wdr, grandfathered status — known before the IMA’s founding, named in 1953.
Found in the oxidized portion of a metamorphosed stratiform zinc orebody (Sterling Hill, New Jersey, USA); in massive manganese ores (Sandur, India); in the oxidized zone of a Ag-Pb-Zn ore deposit (Lardeau, Canada).
It is found associated with Franklinite, chalcophanite (Sterling Hill, New Jersey, USA); pyrolusite, cryptomelane (Sandur, India); smithsonite, gunningite, hydrozincite.
The mineral was named to honor Samuel Woodruff, American miner for the New Jersey Zinc Company, and prolific mineral collector of Franklin-Sterling Hill minerals.