Nelenite Locality: Trotter Mine (Lehigh Mine), Franklin , Franklin Mining District, Sussex County, New Jersey , USA ( Locality at mindat.org ) Size: 4.0 x 2.8 x 1.7 cm. Nelenite is a very rare silicate found in only two localities worldwide, both in the United States and this specimen is from the Type Locality - the Trotter Mine at Franklin, New Jersey. Brown nelenite is richly dispersed on both sides of the matrix, which includes metallic, black franklinite. Ex. George Elling Collection, a noted Franklin/Sterling Hill collector. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Nelenite
A rare manganese-iron phyllosilicate-arsenate known from Franklin Furnace, New Jersey.
Intro adapted from Wikipedia (CC BY-SA).
Nelenite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₁₆As³⁺₃Si₁₂O₃₆(OH)₁₇.
It crystallizes in the monoclinic crystal system (space group R-3m). It is a member of the Pyrosmalite, Clay structural group.
Key properties: Mohs hardness 5; specific gravity 3.46; Light brown streak; Vitreous on cleavages, resinous and duller on fractures luster; optically uniaxial.
IMA symbol Nln, IMA status: approved, named in 1982.
Found in a metamorphosed stratiform zinc deposit, within pegmatitic textured masses, and as calcite-cemented fragments in a breccia probably derived from the pegmatitic material.
It is found associated with Actinolite, calcite, willemite, tirodite, rhodonite, apatite, lennilenapeite, stilpnomelane, microcline, talc.
In honor of Joseph A. Nelen, chemist at the Smithsonian Institution, Washington, D.C., USA.