Geology Reference
In-Depth Information
Common naturally occurring sulphur compounds include the sulphide minerals
cinnabar HgS, galena PbS, sphalerite ZnS, stibnite Sb
2
S
3
and the sulphates gyp-
sum CaSO
4
2H
2
O, alunite KAl
3
(SO
4
)
2
(OH)
6
and barite BaSO
4
.
Its main compound is sulphuric acid H
2
SO
4
, one of the most important sub-
stances in industrial and fertiliser complexes. So important in fact, that the yearly
consumption of sulphuric acid is used as an index to indicate a given nation's
industrial development. Sulphur is also used in batteries, detergents, fungicides,
manufacture of fertilisers, gunpowder, matches, fireworks and corrosion-resistant
concrete.
B.2.63 Tantalum
Tantalum is a hard transition metal highly corrosion-resistant and a good conductor
of heat and electricity. It occurs together with niobium. The chief mineral for Ta is
known as tantalite FeTa
2
O
6
. Deposits are widespread but rarely very concentrated.
Microlite and euxenite are the other minor ores for Ta.
The major use for tantalum is in the manufacture of electronic components,
mainly capacitors. Additionally, it is used for handling corrosive chemicals and in
high-temperature applications - it is subsequently found in aircraft engines.
B.2.64 Tellurium
Tellurium is a semiconductor and a relatively rare element. Its chemistry is similar
to that of sulphur and it has properties typical to both metals and non-metals
alike. Commercial tellurium comes as a byproduct of copper processing. Samples
of tellurium can be found uncombined in Nature but are extremely rare. There
exists some tellurium minerals such as calaverite, sylvanite or tellurite but none are
mined as such.
Tellurium is used as an additive to steel and it is often alloyed with aluminium,
copper, lead or tin. It can also be used in cast iron, ceramics, blasting caps, solar
panels or rubber.
B.2.65 Terbium
Terbium is extensively used in compact fluorescent lamps and phosphors. It intensi-
fies the yellow-green, violet and blue colours. It has been broadly used in solid state
electronics for naval sonar systems, sensors, transducers, mechanical resonators,
high precision fuel injectors and a variety of magneto-mechanical devices. Terbium
is also used as a dopant in solid state devices and crystal stabilisers for fuel cells.
Its high demand, mainly for phosphors, puts this very scarce metal (less than 1%
by mass of REO) in a critical situation. Terbium is expected to constitute a 0.2%
world supply share of REE in 2015. For more details see Sec. B.2.50.
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