Nelenite

Nelenite
Nelenite (brown) and franklinite (metallic, black), from Franklin, Franklin Mining District, Sussex County, New Jersey, US
General
Category	Phyllosilicate
Formula (repeating unit)	(Mn,Fe)16As3Si12O36(OH)17 or (Mn,Fe)16(Si12O30)(OH)14[As3+3O6(OH)3]
IMA symbol	Nln[1]
Strunz classification	9.EE.15
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/m
Unit cell	a = 23.24, b = 13.41 c = 7.38 [Å]; β = 105.21°; Z = 2
Identification
Color	Light to medium brown
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 (-)
Refractive index	nω = 1.718 nε = 1.700
Birefringence	δ = 0.018
Pleochroism	Visible ε = colorless and ω = light brown
References	[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, , rhodonite, apatite, , stilpnomelane, microcline and talc.^[4]

References[]

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