Manganite, a manganese oxide hydroxide mineral, was first reported from Sterling Hill by Palache (1928a), but he subsequently (1935) gave a precise locality in the Franklin Mine for these manganite crystals in andradite. This is likely the first report of the then-unrecognized groutite assemblage. Most local specimens labeled manganite are in fact groutite. True manganite does occur rarely at Franklin, as microscopic crystals forming dark reddish brown velvety coatings in solution vugs in the more abundant of the groutite assemblages described herein.
Preliminary analysis of this material indicates that SiO2, Sb2O5, Fe2O3, and ZnO are all present in amounts less than 1.0 wt. % and that Mg is absent. Manganite is a rare mineral locally. (Dunn, 1995)

 Location Found: Franklin
 Year Discovered: 1827
 Formula: Mn3+O(OH)
 Essential Elements: Hydrogen, Manganese, Oxygen
 All Elements in Formula: Hydrogen, Manganese, Oxygen
 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   Manganite

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.600

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.66

The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 28, No. 2 - Fall 1987, pg. 5Kentrolite, Groutite, Manganite, and Hausmannite From Franklin, New Jersey: Some Observations, Dr. Pete J. Dunn, Groutite, Manganite, Hausmannite
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