Cryptomelane, a potassium manganese oxide mineral, was first described from Sterling Hill by Frondel (1953) and has been subsequently verified by [Dunn]. It has not been reported from Franklin. It occurs in dense to friable botryoidal masses up to 2 cm, is black or brown, and may be quite hard relative to friable manganese oxides. No data exist; the mineral is best identified using X-ray and chemical methods. It is found associated with franklinite and chalcophanite from the pits and mud-zone at Sterling Hill. The general assemblage is the same as that for woodruffite, chalcophanite, and the other associated Mn-oxides. (Dunn, 1995)

 Location Found: Ogdensburg
 Formula: K(Mn74+Mn3+)O16
 Essential Elements: Manganese, Oxygen, Potassium
 All Elements in Formula: Manganese, Oxygen, Potassium
 IMA Status: Approved 1982
 To find out more about this mineral at minDat's website, follow this link   Cryptomelane

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.591

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.52

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