- Chemical Formula: (Fe, Mn)(Ta, Nb)2O6,
Iron Manganese Tantalum Niobium Oxide.
- Class: Oxides
- Uses: An ore of tantalum and niobium and as mineral specimens.
Tantalite is the most widespread tantalum mineral and makes for an important
ore of 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
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 granitic pegmatites rich in lithium and phosphorus minerals
with columbite concentrated at the edges of the pegmatite and tantalite
enriched in the core.
Tantalite has a series of its own. The iron and manganese amounts vary
considerably without much effect on properties. However the two end members
are recognized as distinct minerals although collectors have found this
to be rather cumbersome and generally prefer tantalite to the non-unique
names of ferrotantalite and manganotantalite.
Tantalite has a dimorphic relationship to another mineral called
A dimorph is a mineral that has the same chemistry but a different structure.
Tapiolite has a tetragonal structure as opposed to the orthorhombic structure
of tantalite although it has exactly the same chemistry,
(Fe, Mn)(Ta, Nb)2O6.
As mineral specimens, tantalite can be a nice addition to one's collection.
Good crystals are both complex and handsome. Although the color selection
is usually limited too black to brown the luster is generally good. Manganese
rich tantalites can be brown and translucent.
Color is dark black, iron-black to dark brown or even reddish
Luster is submetallic to almost resinous.
Transparency: Crystals are nearly opaque being transparent in
Crystal System is orthorhombic; 2/m 2/m 2/m
Crystal Habits include stubby prismatic crystals with complexly
faceted or rounded terminations. Also very flat tabular crystals sometimes
aggregated together in parallel or nearly parallel groups. Can also be
granular and massive.
Cleavage is good in one direction.
Fracture is subconchoidal.
Hardness is 6 - 6.5
Specific Gravity is approximately 8.0+ when pure (very heavy
for non-metallic minerals).
Streak is brownish-red to black.
Other Characteristics: Some specimens may show a bluish iridescent
tarnish and demonstrate weak magnetism.
Associated Minerals include
Notable Occurrences include Newry, Maine; San Diego Co., California;
Colorado and Amelia, Virginia, USA; Renfrow County, Ontario, Canada; Madagascar;
Sweden; Norway and Finland.
Best Field Indicators are crystal habit, streak, associations
and specific gravity.