This metal seems quite interesting:
QUOTE
Tantalum is a greyish silver, heavy, and very hard metal. When pure, it is ductile and can be drawn into fine wire, which can be used as a filament for evaporating metals such as aluminium. Tantalum is almost completely immune to chemical attack at temperatures below 150°C, and is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulphur trioxide. The element has a melting point exceeded only by tungsten and rhenium.
Isolation
Here is a brief summary of the isolation of tantalum.
Isolation of tantalum appears to be complicated. Tantalum minerals usually contain both niobium and tantalum. Since they are so similar chemically, it is difficult to separate them. Tantalum can be extracted from the ores by first fusing the ore with alkali, and then extracting the resultant mixture into hydrofluoric acid, HF. Current methodology involves the separation of tantalum from these acid solutions using a liquid-liquid extraction technique. In this process tantalum salts are extracted into the ketone MIBK (methyl isobutyl ketone, 4-methyl pentan-2-one). The niobium remains in the HF solution.
After conversion to the oxide, metallic tantalum can be made by reduction with sodium or carbon. Electrolysis of molten fluorides is also used.
QUOTE
Sources:
Chiefly occurs in the mineral tantalite. Always found with niobium. Annual world production is around 840 tons. Primary mining areas are Australia, Zaire, Brazil, Russia, Norway, Canada and Madagascar.
Uses:
Used in metal alloys. Tantalum pentoxide is used in capacitors, condensers, cutting tools, vacuum tube filaments and in camera lenses to increase refracting power.
I guess the mineral was mined from Russia?
I highly doubt that Kazak coins are minted in Russia. They seem to have a mint of their own.
Too bad that's way too pricy else it would have been one in my list.
