Ferberite

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Ferberite
Panasqueira Fluorapatite Ferberite.jpg
Fluorapatite on ferberite from Minas da Panasqueira, Beira Baixa, Portugal
General
Category Tungstate mineral
Formula
(repeating unit)
FeWO4
Strunz classification 04.DB.30
Crystal symmetry Monoclinic prismatic
H-M symbol: (2/m)
Space group: P 2/c
Unit cell a = 4.72 Å, b = 5.7 Å, c = 4.96 Å; β = 90°; Z=2
Identification
Color Black, dark brown in transmitted light
Crystal habit Bladed crystals; massive
Crystal system Monoclinic
Twinning Contact or interpenetrant or lamellar twins
Cleavage Perfect on {010}; partings on {100} and {102}
Fracture Uneven
Tenacity Brittle
Mohs scale hardness 4–4.5
Luster Submetallic to metallic adamantine
Streak Brownish black
Diaphaneity Nearly to entirely opaque
Specific gravity 7.58
Optical properties Biaxial (+)
Refractive index nα = 2.255 nβ = 2.305 nγ = 2.414
Birefringence δ = 0.159
2V angle Measured: 66°
Other characteristics Slightly magnetic
References [1][2][3]

Ferberite is the iron endmember of the manganese - iron wolframite solid solution series. The manganese endmember is hübnerite. Ferberite is a black monoclinic mineral composed of iron(II) tungstate, FeWO4.

Ferberite and hübnerite often contain both divalent cations of iron and manganese, with wolframite as the intermediate species for which the solid solution series is named.[4]

Ferberite occurs as granular masses and as slender prismatic crystals. It has a Mohs hardness of 4.5 and a specific gravity of 7.4 to 7.5. Ferberite typically occurs in pegmatites, granitic greisens, and high temperature hydrothermal deposits.[1] It is a minor ore of tungsten.

Ferberite was discovered in 1863 in Sierra Almagrera, Spain, and named after the German minerologist Moritz Rudolph Ferber (1805–1875).[2]

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