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Columbite-(Fe)  (Ferrocolumbite)
Current inventory:  0 gems
 

Chemistry:  Fe²⁺Nb₂O₆  [Iron Niobium Oxide]

Discovered in 1928;   IMA status: Valid (pre-IMA; Grandfathered).
Ferrocolumbite is named after the Latin word "ferrium" for "iron" and its content of the element niobium, formerly called "columbium".

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.18-30

Nickel-Strunz 10th Ed. ID:

4.DB.35

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
B : With medium-sized cations; chains of edge-sharing octahedra

Related to:

Columbite Group. Ferrocolumbite - Ferrotantalite Series. Ferrocolumbite - Manganocolumbite Series.

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Crystals short prismatic or equant, also flat tabular, to 0.75 m. In groups of parallel or subparallel crystals, to 18 t; massive.

Twinning:

Common as heart-shaped contact and penetration twins, on {021} and {023}, may produce pseudohexagonal trillings. More rarely on {051} and {15•1•0}.

Physical Properties

Cleavage:

[100] Distinct, [010] less Distinct

Fracture:

Irregular/Uneven, Sub-Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

6.0

Density:

5.20 - 6.65 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Paramagnetic

Optical Properties

Color:

Black to Brownish Black; Reddish Brown in transmitted light. Commonly tarnishes to iridenscent.

Transparency:

Opaque. Translucent on thin edges

Luster:

Vitreous, Sub-Metallic

Refractive Index:

R1–R2: (400) 18.4–19.1, (420) 17.7–18.6, (440) 17.3–18.2, (460) 17.1–17.9, (480) 16.9–17.7, (500) 16.9–17.6, (520) 16.8–17.5, (540) 16.8–17.4, (560) 16.7–17.3, (580) 16.7–17.2, (600) 16.7–17.2, (620) 16.6–17.1, (640) 16.5–17.1, (660) 16.4–16.9, (680) 16.3–16.8, (700) 16.1–16.8

Biaxial ( - )

Birefringence:

0.00 - 0.00

Dispersion:

Relatively Strong; r < v

Pleochroism:

None

Anisotrophism:

In reflected light, grayish white with a brownish tint and reddish internal reflections.

Occurances

Geological Setting:

An accessory constituent of granite pegmatites; rarely in carbonatites; a detrital mineral in placer deposits.

Common Associations:

Albite, Amblygonite, Apatite, Beryl, Cassiterite, Lepidolite, Lithiophilite, Microline, Microlite, Muscovite, Samarskite, Spodumene, Tourmaline, Triphylite, Triplite

Type Locality:

Green's Well pegmatite, Wodgina, Pilbara Region, Western Australia, Australia

Year Discovered:

1928

View mineral photos:

Columbite-(Fe) Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Columbite-(Fe), or Ferrocolumbite, is a fairly common mineral but rarely faceted because it is opaque black. It can be somewhat attractive when it tarnishes and becomes iredescent. It is another of the Black Gems for collectors of the unusual. Ferrocolumbite is relatively hard with a Mohs hardness of 6.0 and very dense at 5.20 - 6.65.

There are a number of notable locatoins worldwide for finding Columbite-(Fe): in the USA, in Connecticut, at Middletown, Portland, and Haddam, Middlesex County; large masses from the Beecher Lode, eight km southeast of Custer, Custer County, and around Keystone, Pennington County, South Dakota; in the Spruce Pine district, Mitchell Co., and the Foote mine, Kings Mountain, Cleveland County, North Carolina. At Ånneröd, Tveit, and elsewhere in Norway. In Russia, from Miass, Ilmen Mountains, Southern Ural Mountains. At Craveggia, Val Vigezzo, Piedmont, Italy. Large crystals from Ambatofotsikely and Antsirabe, Madagascar. At Greens Well, Wodgina, Greenbushes, and elsewhere in Western Australia. In the Ishikawa district, Fukushima Prefecture, Japan.
 

  
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