COLUMBINE, an erect perennial herbaceous plant known botanically as Aquilegia vulgaris (natural order Ranunculaceae). In Med. Latin it was known as Columbina sc. herba, the dove’s plant. The slender stem bears delicate, long-stalked, deeply divided leaves with blunt segments, and a loose panicle of handsome drooping blue or white flowers, which are characterized by having all the five petals spurred. The plant occurs wild in woods and thickets in England and Ireland, and flowers in early summer. It is well known in cultivation as a favourite spring flower, in many varieties, some of which have red flowers.
| Crystal of Columbite. |
COLUMBITE, a rare mineral consisting of iron niobate, FeNb2O6, in which the iron and niobium are replaced by varying amounts of manganese and tantalum respectively, the general formula being (Fe, Mn) (Nb, Ta)2O6. It was in this mineral that Charles Hatchett discovered, in 1801, the element niobium, which he himself called columbium after the country (Columbia or America) whence came the specimen in the British Museum collection which he examined. The species has also been called niobite. It crystallizes in the orthorhombic system, and the black, opaque crystals are often very brilliant with a sub-metallic lustre. Twinned crystals are not uncommon, and there is a distinct cleavage parallel to the face marked b in the figure. Hardness 6; specific gravity 5.3. With increasing amount of tantalum the specific gravity increases up to 7.3, and members at this end of the series are known as tantalite (FeTa2O6). Specimens in which the iron is largely replaced by manganese are known as manganocolumbite or manganotantalite, according as they contain more niobium or more tantalum. Columbite occurs as crystals and compact masses in granite and pegmatite at Rabenstein in Lower Bavaria, the Ilmen Mountains in the Urals, Haddam in Connecticut, and several other localities in the United States; also in the cryolite of Greenland. Tantalite is from Finland, and it has recently been found in some abundance in the deposits of cassiterite in the tin-field of Greenbushes in the Blackwood district, Western Australia.
Dimorphous with columbite and tantalite are the tetragonal minerals tapiolite (= skogbölite) and mossite, so that the four form an isodimorphous group with the general formula (Fe, Mn) (Nb, Ta)2O6. Mossite is from a pegmatite vein near Moss in Norway, and tapiolite is from Finland. All these minerals contain tin in small amount.
(L. J. S.)
COLUMBIUM, or Niobium (symbol Cb or Nb, atomic weight 94), one of the metallic elements of the nitrogen group, first detected in 1801 by C. Hatchett in a specimen of columbite (niobite) from Massachusetts (Phil. Trans. 1802, 49). It is usually found associated with tantalum, the chief minerals containing these two elements being tantalite, columbite, fergusonite and yttrotantalite; it is also a constituent of pyrochlor, euxenite and samarskite. Columbium compounds are usually prepared by fusing columbite with an excess of acid potassium sulphate, boiling out the fused mass with much water, and removing tin and tungsten from the residue by digestion with ammonium sulphide, any iron present being simultaneously converted into ferrous sulphide. The residue is washed, extracted by dilute hydrochloric acid, and again well washed with boiling water. It is then dissolved in hydrofluoric acid and heated in order to expel silicon fluoride; finally the columbium, tantalum and titanium fluorides are separated by the different solubilities of their double fluorides (C. Marignac, Ann. chim. et phys. 1866 [4], 8, p. 63; 1868, 13, p. 28; see also W. Gibbs, Jahresb. 1864, p. 685; R. D. Hall and E. F. Smith, Proc. Amer. Philos. Soc. 1905, 44, p. 177).
The metal was first obtained by C. W. Blomstrand (Journ. prak. Chem. 1866, 97, p. 37) by reducing the chloride with hydrogen; it has more recently been prepared by H. Moissan by reducing the oxide with carbon in the electric furnace (the product obtained always contains from 2-3% of combined carbon), and by H. Goldschmidt and C. Vautin (Journ. Soc. Chem. Industry, 1898, 19, p. 543) by reducing the oxide with aluminium powder. As obtained by the reduction of the chloride, it is a steel grey powder of specific gravity 7.06. It burns on heating in air; and is scarcely attacked by hydrochloric or nitric acids, or by aqua regia; it is soluble in warm concentrated sulphuric acid.