THE MINERAL COLUMBITE

  • Chemical Formula: (Fe, Mn, Mg)(Nb, Ta)2O6, Iron Manganese Magnesium Niobium Tantalum Oxide.
  • Class: Oxides and Hydroxides
  • Uses: An ore of niobium and tantalum and as mineral specimens.
  • Specimens

Columbite is the most widespread niobium mineral and makes for an important ore of the industrially useful metal. Niobium, Nb, is used in alloys for improved strength. It also has shown superconductive properties and is being studied with other metals for a possible breakthrough alloy in this new industrial field.

Niobium had previously been called columbium hence the name columbite. The official name was made niobium in the 1950's after a century of debate, although some groups still do not recognize the official name and still refer to it as columbite. Of course most geologists still refer to its name sake mineral as columbite instead of the proposed "niobite".

Columbite forms a series with the mineral tantalite. In fact the two are often grouped together as a semi-singular mineral called columbite-tantalite in many mineral guides. A series is where two or more elements can occupy the same places within a crystal structure and their respective percentages can then vary. Columbite is the more niobium rich end member and tantalite is the more tantalum rich end member. The two minerals of this series have similar properties since they have the same structure and similar chemistries (tantalum and niobium are very similar elements).

Tantalite's greatest difference from columbite is its much higher specific gravity, 8.0+ compared to columbite's 5.2. Other properties that vary slightly are color, transparency and streak. Both minerals can be found more or less together in granitic pegmatites rich in lithium and phosphorus minerals with columbite concentrated at the edges of the pegmatite and tantalite enriched in the core.

Columbite is a series within a series. The iron, manganese and magnesium amounts vary considerably without much effect on properties. However the end members are recognized as distinct minerals although collectors have found this to be rather cumbersome and generally prefer columbite to the non-unique names of ferrocolumbite, manganocolumbite and magnocolumbite.

As mineral specimens, columbite can be a nice addition to one's collection. Good crystals are both complex and handsome. Although the color selection is usually limited too black to brown the luster is generally good.

PHYSICAL CHARACTERISTICS:

  • Color is dark black, iron-black to dark brown.
  • Luster is submetallic.
  • Transparency: Crystals are nearly opaque being transparent in thin splinters.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include stubby prismatic crystals with complexly faceted or rounded terminations. Also very flat tabular crystals often aggregated together in parallel or nearly parallel groups. Can also be granular and massive.
  • Cleavage is good in one direction.
  • Fracture is subconchoidal.
  • Hardness is 6
  • Specific Gravity is approximately 5.0 to 5.3+ when near pure columbite (very heavy for non-metallic minerals).
  • Streak is brown to black.
  • Other Characteristics: Some specimens may demonstrate weak magnetism.
  • Associated Minerals include albite, spodumene, cassiterite, microcline, lepidolite, apatite, beryl, microlite, tourmalines and amblygonite.
  • Notable Occurrences include Newry, Maine; San Diego Co., California; Colorado and Amelia, Virginia, USA; Renfrow County, Ontario, Canada; Madagascar; Sweden; Norway; Brazil; Argentina; Kugi-Lyal, Pamir, Russia and Finland.
  • Best Field Indicators are crystal habit, streak, associations and specific gravity.
COLUMBITE specimens:
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COLUMBITE specimen clm-1
$ 60.00
Dims: 2.3 x 1.6 x 1.0" (5.8 x 4.1 x 2.6 cm)
Wt: 8.0 oz. (228 g)
Londonderry, Western Australia
The largest Columbite crystal that I have yet seen comprises this hand specimen- apart from a small amount of white host rock and a small book of mica, it consists entirely of Columbite. The crystal is in fair condition, as it shows substantial old breakage and is not quite complete, and its orthorhombic prismatic form is warped. The crystal is black in color, has a dull, waxy luster, and is, of course, opaque.
no photo
clm-1 ($ 60.00)
Londonderry, Western Australia
COLUMBITE specimen clm-2
$ 141.00
Dims: 1.4 x 1.2 x 0.8" (3.5 x 3.1 x 2.0 cm)
Wt: 19 g
Darrah Pech, Kunar Province, Afghanistan
Two Columbite blades are partly embedded in the aquamarine base of this large thumbnail specimen. These crystals have dimensions of 0.4 x 0.3 x 0.1" (1.1 x 0.8 x 0.1 cm) and 0.3 x 0.2 x 0.1" (7 x 5 x 1 mm), and both are in excellent condition, showing no fresh damage. Their orthorhombic bladed form is quite good, and each one has a brown-black coloration and a greasy-to-pearly luster. They are accompanied by several small albite blades that are also embedded in the aquamarine base. This base has a few partial crystal faces and shows no fresh damage- even its broken areas have undergone partial healing. It is cloudy but has a beautiful pale blue color.
no photo
clm-2 ($141.00)
Darrah Pech, Kunar Province, Afghanistan
COLUMBITE specimen clm-3
$ 57.00
Dims: 1.4 x 1.1 x 0.8" (3.5 x 2.8 x 2.1 cm)
Wt: 1.2 oz. (35 g)
Nuristan, Afghanistan
A single, moderately well-formed Columbite crystal makes up the bulk of this hand specimen. The crystal has dimensions of 1.3 x 1.1 x 0.4" (3.2 x 2.8 x 1.0 cm) and though it has been broken, it has been repaired quite well. Its orthorhombic prismatic form is not quite complete but is still quite good, and its nearly black color with red highlights makes me think that it is of the variety Manganocolumbite. Its submetallic luster is standard for the specie and it is essentially opaque. A few broken mica books and some broken feldspar are attached.
no photo
clm-3 ($ 57.00)
Nuristan, Afghanistan
COLUMBITE specimen clm-4
$ 72.00
Dims: 1.7 x 1.3 x 0.9" (4.4 x 3.3 x 2.4 cm)
Wt: 4.0 oz. (114 g)
Golconda Mine, Governador Valadares, Minas Gerais, Brazil
This piece consists of a single, loose Columbite crystal that is in good condition, showing light fresh damage only at its base. Its orthorhombic prismatic form is moderately well-defined, though the crystal is somewhat warped and shows considerable healed damage. Its gray-black color and dull, submetallic luster are standard for its specie. There is no host rock present.
no photo
clm-4 ($ 72.00)
Golconda Mine, Governador Valadares, Minas Gerais, Brazil
COLUMBITE specimen clm-5
$ 25.00
Dims: 1.3 x 0.9 x 0.8" (3.2 x 2.3 x 1.9 cm)
Wt: 1.6 oz. (45 g)
Spargoville, Western Australia
This large thumbnail piece consists of a single Columbite crystal that is in good condition, showing only a small amount of fresh damage. Its orthorhombic form is well-defined but somewhat warped, and it has the standard black color and a dull, pearly-to-waxy luster. It is slightly rust-stained in some areas, and a small amount of quartz or feldspar is attached.
no photo
clm-5 ($ 25.00)
Spargoville, Western Australia
COLUMBITE specimen clm-6
$ 25.00
Dims: 1.2 x 1.0 x 0.5" (3.1 x 2.4 x 1.3 cm)
Wt: 1.4 oz. (40 g)
Spargoville, Western Australia
A single Columbite crystal comprises this thumbnail specimen. It is in excellent condition, showing no fresh damage, and has excellent orthorhombic prismatic form, though old damage has destroyed a few edges. It has the standard black color of the specie and a dull, waxy luster, and is rust-stained and completely opaque. A small amount of either broken quartz or feldspar is present, but this is not appreciable.
no photo
clm-6 ($ 25.00)
Spargoville, Western Australia

 


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