Tantalite

Tantalum is found mainly in the minerals tantalite [(Fe,Mn)Ta2O6] (easily confused with columbite, the niobium analogue of tantalite) and euxenite. Ores are found in Australia, Brazil, Mozambique, Thailand, Portugal, Nigeria, Congo,Canada and Tanzania. It is also a byproduct from the extraction of tin.

Tantalite is the most spread tantalum mineral and makes for an important ore for the industrially useful metal. Tantalum is used in alloys for strength and higher melting points, in glass to increase the index of refraction, and in surgical steel, as it is non-reactive and non-irritating to body tissues.

Tantalite forms a series with the mineral columbite. In fact the two are often grouped together as a semi-singular mineral called columbite-tantalite in many mineral guides. A series is where two or more elements can occupy the same places within a crystal structure and their respective percentages can then vary.

The two minerals of this series have similar properties since they have the same structure and similar chemistries (tantalum and niobium are very similar elements). Tantalite is the more tantalum rich end member and columbite is the more niobium rich end member. Niobium had been called columbium hence the name columbite.

Tantalite?s greatest difference from columbite is its much greater specific gravity, 8.0+ compared to columbite?s 5.2. Other properties that vary slightly are color, transparency and streak. Both minerals can be found more or less together in granite pegmatite?s rich in lithium and phosphorus minerals with columbite concentrated at the edges of the pegmatite and tantalite enriched in the core.

PHYSICAL CHARACTERISTICS

Color	Dark black, iron-black to dark brown or even reddish brown
Luster	Submetallic to almost resinous
Transparency	Crystals are nearly opaque being transparent in thin splinters.
Crystal System	Orthorhombic; 2/m 2/m 2/m
Crystal Habits	stubby prismatic crystals with complexly
Cleavage	Good in one direction
Fracture	Subconchoidal
Hardness	6 - 6.5
Specific Gravity	Approximately 8.0+ when pure (very heavy for non-metallic minerals)
Streak	Brownish-red to black
Other Characteristics	Some specimens may show a bluish iridescent tarnish and demonstrate weak magnetism

Associated Minerals	albite, spodumene, cassiterite, microcline, lepidolite, apatite, beryl, microkite, tourmalines and amblygonite
Best Field Indicators	Crystal habit, steak, associations and specific gravity