Columbite, also called niobite, niobite-tantalite and columbate [], is a black mineral group that is an ore of

niobium Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...

. It has a submetallic Lustre (mineralogy), luster and a high density and is a niobate of iron and manganese. This mineral group was first found in Haddam, Connecticut, in the United States. It forms a series with the tantalum-dominant analogue

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and one with the manganese-dominant analogue manganocolumbite. The iron-rich member of the columbite group is ferrocolumbite. Some tin and tungsten may be present in the mineral. Yttrocolumbite is the yttrium-rich columbite with the formula . It is a radioactive mineral found in Mozambique. Columbite has the same composition and crystal symmetry (

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

) as tantalite. In fact, the two are often grouped together as a semi-singular mineral series called

columbite-tantalite Coltan (short for columbite–tantalites and known industrially as tantalite) is a dull black metallic ore from which the elements niobium and tantalum are extracted. The niobium-dominant mineral in coltan is columbite (after niobium's original A ...

or coltan in many mineral guides. However, tantalite has a much greater specific gravity than columbite, more than 8.0 compared to columbite's 5.2. Columbite is also very similar to tapiolite. Those minerals have same chemical composition but different crystal symmetry: orthorhombic for columbite and tetragonal for tapiolite. The largest documented single crystal of columbite consisted of plates thick measuring . Columbite contains varying amounts of thorium and uranium, which makes it radioactive to various degrees.

History and etymology

The occurrence of columbite in the United States was made known from a specimen presumably stemming from John Winthrop (1606–1676), first Governor of the

Connecticut Colony The ''Connecticut Colony'' or ''Colony of Connecticut'', originally known as the Connecticut River Colony or simply the River Colony, was an English colony in New England which later became Connecticut. It was organized on March 3, 1636 as a settl ...

and avid mineral collector. Amidst 600 other samples, it was donated by his namesake and grandson, John Winthrop (1681–1747) to Hans Sloane, President of the Royal Society of London, upon becoming a Fellow of the Royal Society in 1737. In 1801

Charles Hatchett Charles Hatchett FRS FRSE (2 January 1765 – 10 March 1847) was an English mineralogist and analytical chemist who discovered the element niobium, for which he proposed the name "columbium". Hatchett was elected a Fellow of the Linnaean Societ ...

discovered the element

in this specimen, which he named columbium in honour of explorer Christopher Columbus.

References

External links

* Iron(II) minerals Manganese(II) minerals Niobium minerals Orthorhombic minerals Minerals in space group 60 Oxide minerals Tantalum minerals {{oxide-mineral-stub

History and etymology

See also

References

External links