Английская Википедия:Columbite
Шаблон:Short description Шаблон:Infobox mineral Columbite, also called niobite, niobite-tantalite and columbate, with a general chemical formula of Шаблон:Chem2, is a black mineral group that is an ore of niobium. It has a submetallic luster, a high density, and is a niobate of iron and manganese. It forms a series with the tantalum-dominant analogue ferrotantalite and one with the manganese-dominant analogue manganocolumbite. The iron-rich member of the columbite group is ferrocolumbite, where some tin and tungsten may be present in the mineral. Yttrocolumbite is the yttrium-rich columbite with the formula Шаблон:Chem, is a radioactive mineral found in Mozambique.[1]
Columbite has the same composition and crystal symmetry (orthorhombic) as tantalite.[2] In fact, the two are often grouped together as a semi-singular mineral series called columbite-tantalite 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.[3]
Columbite is also very similar to tapiolite. These minerals have the same chemical composition but different crystal symmetry: orthorhombic for columbite and tetragonal for tapiolite.[4] The largest documented single crystal of columbite consisted of plates Шаблон:Convert thick measuring Шаблон:Convert.[5]
Columbite contains varying amounts of thorium and uranium, which makes it radioactive to various degrees.[6]
History and etymology
This mineral group was first found in Haddam, Connecticut, in the United States.[7] 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 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.[8]
In 1801, Charles Hatchett discovered the element niobium in this specimen,[9] which he named columbium in honour of explorer Christopher Columbus.[10]
See also
References
External links
Шаблон:Manganese minerals Шаблон:Ores Шаблон:Authority control
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ mindat.org Tantalite
- ↑ P. Cerny et al. "The tantalite-tapiolite gap: natural assemblages versus experimental data" Canadian Mineralogist 30 (1992) 587 free download
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite book
