Nelenite

(Mn,Fe)₁₆As₃Si₁₂O₃₆(OH)₁₇ or
(Mn,Fe)₁₆(Si₁₂O₃₀)(OH)₁₄[As³⁺₃O₆(OH)₃]IMA symbolNln^[1]Strunz classification9.EE.15Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupC2/mUnit cella = 23.24, b = 13.41
c = 7.38 [Å]; β = 105.21°; Z = 2IdentificationColorLight to medium brownCrystal habitCoarsely granular to massiveCleavagePerfect on {0001}Mohs scale hardness5LusterVitreous, resinousStreakLight brownDiaphaneityTransparentSpecific gravity3.46Optical propertiesUniaxial (-)Refractive indexn_ω = 1.718 n_ε = 1.700Birefringenceδ = 0.018PleochroismVisible ε = colorless and ω = light brownReferences^[2][3][4]

Nelenite is a rare manganese iron phyllosilicate arsenate mineral found in Franklin Furnace, New Jersey.

Its chemical formula is (Mn,Fe)₁₆As₃Si₁₂O₃₆(OH)₁₇ or (Mn,Fe)₁₆(Si₁₂O₃₀)(OH)₁₄[As³⁺₃O₆(OH)₃]^[2]

Discovery and occurrence

It was first describe in 1984 for an occurrence in the Trotter Mine, Franklin Mining District, Sussex County, New Jersey. It was named for Joseph A. Nelen of the Smithsonian Institution.^[2][4] It has also been reported from Montgomery County, Virginia and the Suceava district of Romania.^[2] At the type locality in New Jersey it occurs associated with actinolite, calcite, willemite, tirodite, rhodonite, apatite, lennilenapeite, stilpnomelane, microcline and talc.^[4]

References