Nelenite

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Nelenite
Nelenite-213099.jpg
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]
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 [1][2][3]

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

Its formula is (Mn,Fe)16As3Si12O36(OH)17[3] or (Mn,Fe)16(Si12O30)(OH)14[As3+3O6(OH)3][1]

Discovery and occurrence[edit]

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.[1][3] It has also been reported from Montgomery County, Virginia and the Suceava district of Romania.[1] At the type locality in New Jersey it occurs associated with actinolite, calcite, willemite, tirodite, rhodonite, apatite, lennilenapeite, stilpnomelane, microcline and talc.[3]

References[edit]