|Structure: Othorhombic|Composition: Iron Manganese |Moh's Hardness:-
Columbite/Tantalite
This curious mineral only came to light to Silk Pixie in January 2023, when sent as a rare gem on a gemstone auction site.
Niobium, we HAVE heard of and used. This metal along with titanium and aluminium, can be anodised, ie dipped in an electrified acid bath, to change colour.
The vivid coloured stone shown is a firey "manganotantalite", very eyecatching and we need to find out more about this rare stone, currently (Jan 2023) priced at around £400.
columbite, hard, black (often iridescent), heavy oxide mineral of iron, manganese, and niobium, (Fe, Mn)Nb2O6. Tantalum atoms replace niobium atoms in the crystal structure to form the mineral tantalite, which is similar but much more dense. These minerals are the most abundant and widespread of the naturally occurring niobates and tantalates and are important ores, their elements niobium and tantalum serving as constituents of corrosion-resistant metal alloys. Columbite and tantalite are found together in granite, pegmatites, and placer deposits. They occur abundantly in western Australia. By the early 21st century Mozambique had become the world’s largest extractor of tantalum and Brazil the largest producer of niobium. Formerly called columbium, niobium was first recognized in columbite and was originally named after the mineral. For detailed physical properties, see oxide mineral (table).
tantalite, tantalum-rich variety of the mineral columbite (q.v.) with the chemical formula (Fe,Mn)(Ta,Nb)2O6. Tantalite is the principal ore of the metal tantalum.
