Geology Reference
In-Depth Information
material for immersion lithography because of its high refractive index. For more
details see Sec. B.2.50.
B.2.36 Magnesium
Magnesium is among the eight most abundant elements. It usually occurs in
crustal rocks typically as insoluble carbonates and sulphates and less accessibly as
silicates. Important magnesium-containing minerals are dolomite CaMg(CO
3
)
2
,
magnesite MgCO
3
, carnallite K
2
MgCl
4
6H
2
O, olivine (Mg;Fe)
2
SiO
4
, talc
Mg
3
Si
4
O
10
(OH)
2
or spinel MgAl
2
O
4
.
It is a light, chemically reactive metal, belonging to the alkaline earth group.
It is known as the lighter structural metal in industry as it is lightweight and has
the capacity to form mechanically resistant alloys. Such alloys are used in beverage
cans, as structural components of vehicles and machinery. Magnesium compounds,
primarily magnesium oxide, are used as refractory materials in furnace linings for
producing iron and steel, nonferrous metals, glass and cement. Magnesium oxide is
used in the agricultural, chemical and construction industries.
B.2.37 Manganese
Manganese is a grey-white chemically active metal. It resembles iron and is essential
in the iron and steel production by virtue of its sulphur-fixing, deoxidising and
alloying properties. Manganese is found in over 300 different and widely distributed
minerals of which about twelve are commercially important. It occurs in primary
deposits as the silicate metal. Of highest commercial importance are the secondary
deposits of oxides and carbonates such as pyrolusite MnO
2
and to a lesser extent
rhodochrosite MnCO
3
. Vast quantities of manganese exist in manganese nodules
(manganese, iron and other metal-containing agglomerates) located on the ocean
bed. No economically viable methods of harvesting in this way has been found to
date.
It is frequently employed in aluminium alloys. Further applications for man-
ganese and its compounds are as a gasoline additive to boost octane rating, as a
reagent in organic chemistry, as a colourising and decolourising agent for glass, as
a paint, as a disinfectant and in batteries.
B.2.38 Mercury
Cinnabar HgS is the only important ore and source of mercury with deposits at Al-
maden in Spain being the most famous and extensive. Mercury is the only common
metal found at liquid state in room temperature. Its high density means, it is used
in barometers and manometers. It is also extensively used in thermometers thanks
to its high rate of thermal expansion that is fairly constant over a wide temperature
range. Amalgams of silver, gold and tin (alloys of mercury) are used in dentistry.
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