Woodruffite is a zinc manganese oxide hydrate mineral and is likely the Zn-analogue of todorokite. Frondel (1953) gave the composition as Na2O 0.06, K2O 0.55, BaO 0.12, MgO 0.62, ZnO 13.89, MnO 7.88, MnO2 64.27, Fe2O3 0.26, Al2O3 0.14, SiO2 0.86, H2O 10.48, total = 99.13 wt. %. No recent analytical studies have been done.
Woodruffite was first described from Sterling Hill by Frondel (1953) and was included in the study of Potter and Rossman (1979). It has not been reported from Franklin.
Woodruffite occurs as massive, very fine-grained masses and crusts with a mammillary to botryoidal surface. It has a dull luster and is opaque and black to brown. Concentric layering is common, and the hardness varies substantially, from 4 1/2 to 1, the latter in pulverent brown massive material. The density is 3.71 g/cm3 (Frondel, 1953). Woodruffite resembles todorokite and other massive Mn-oxides; identification is best done employing X-ray methods. Woodruffite was not studied by [Dunn].
Woodruffite is known from the mud zone at Sterling Hill, mined as the Noble and Passaic Mines in the 1870's and noted for the abundance of hemimorphite and secondary manganese minerals. Woodruffite occurs as dense masses, intimately associated with chalcophanite and residual franklinite. Confirmed specimens are sparse, but some material probably exists mislabeled in systematic and private collections. (Dunn, 1995)

 Location Found: Ogdensburg (Type Locality)
 Year Discovered: 1953
 Formula: Zn(Mn4+,Mn3+)5O10·3½H2O
 Essential Elements: Hydrogen, Manganese, Oxygen, Zinc
 All Elements in Formula: Hydrogen, Manganese, Oxygen, Zinc
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
 To find out more about this mineral at minDat's website, follow this link   Woodruffite

Dunn, Pete J. (1995). Franklin and Sterling Hill New Jersey: the world's most magnificent mineral deposits. Franklin, NJ.: The Franklin-Ogdensburg Mineralogical Society. p.606

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.84

The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 18, No. 1 - March 1977, pg. 13The Post Palache Minerals - Woodruffite
View IssueV. 9, No. 1 - February 1968, pg. 16The Exclusive Minerals of Franklin/Ogdensburg, N.J. (as of January 1968) by Frank Z. Edwards - Woodruffite (Short Note)
View IssueV. 5, No. 2 - August 1964, pg. 13Woodruffite (small article)
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