Geographic Minerals

Nelenite: Properties and Occurrences

Nelenite: Properties and Occurrences

Nelenite is a rare manganese iron phyllosilicate arsenate mineral found in Franklin Furnace, New Jersey. It is a trigonal-hexagonal scalenohedral brown mineral containing arsenic, hydrogen, iron, magnesium, manganese, oxygen, silicon, and zinc. Its formula is (Mn,Fe)16As3Si12O36(OH)17 or (Mn,Fe)16(Si12O30)(OH)14[As33+O6(OH)3]

It is a polymorph of schallerite and a member of the friedelite group. It was Named in 1984 by Pete J. Dunn and Donald R. Peacor in honor of Joseph A. Nelen (28 Aug 1923 – 7 Jun 2005), chemist at the Smithsonian Institution, Washington, D.C., USA, for his contributions contributions “to the chemistry of minerals, in particular his analytical studies of the complex arsenosilicates of manganese which are found at Franklin and Sterling Hill.”

General Information

  • Category: Phyllosilicate
  • Formula: (Mn,Fe)16As3Si12O36(OH)17 or (Mn,Fe)16(Si12O30)(OH)14[As33+O6(OH)3]
  • Crystal system: Monoclinic
  • Crystal class: Prismatic (2/m) (same H-M symbol)
  • Color: Light to medium brown.
Nelenite – a manganese iron arsenic silicate hydroxide mineral


Nelenite is a manganese iron arsenic silicate hydroxide mineral of the friedelite group. In contrast to schallerite, It is distinctly brown; turbid material is light brown. The luster is vitreous. The density is 3.46 g/cm3 (meas.), 3.45 g/cm3 (calc.). Nelenite is not discernibly fluorescent in the ultraviolet.

  • Crystal habit: Coarsely granular to massive
  • Cleavage: Perfect on {0001}
  • Mohs scale hardness: 5
  • Luster: Vitreous, resinous
  • Streak: Light brown
  • Diaphaneity: Transparent
  • Specific gravity: 3.46
  • Optical properties: Uniaxial (-)

Discovery and occurrence

It was first describe in 1984 for an occurrence in the Trotter Mine, Franklin Mining District, Sussex County, New Jersey. It occurs in several parageneses, associated with actinolite, tirodite, albite, garnet, feldspars, and several members of the stilpnomelane group in coarse-grained assemblages with pegmatitic texture and a breccia likely derived from this rock.

Nelenite is named in honour of Joseph A. Nelen, chemist at the Smithsonian Institution. It was named for Joseph A. Nelen of the Smithsonian Institution. It has also been reported from Montgomery County, Virginia and the Suceava district of Romania. At the type locality in New Jersey it occurs associated with actinolite, calcite, willemite, tirodite, rhodonite, apatite, lennilenapeite, stilpnomelane, microcline and talc.

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