Geology Reference
In-Depth Information
B.2.5 Beryllium
Beryllium is a light alkaline-earth metal and has one of the highest melting points
of any light metal. It is relatively scarce occurring as bertrandite Be
4
Si
2
O
7
(OH)
2
,
beryl Be
3
Al
2
Si
6
O
18
, chrysoberyl BeAl
2
O
4
and phenakite Be
2
SiO
4
. Precious forms
of beryl are aquamarine and emerald.
The element is used as an alloying agent in the production of beryllium-copper.
BeCu alloys are used in many applications due to their electrical and thermal
conductivity, high strength and hardness and good stability over a wide temperature
range. Some of them are applied in the defence and aerospace industries, in the
field of X-ray detection diagnostics and in the manufacture of computer equipment.
B.2.6 Bismuth
The most important ores of bismuth are bismuthinite Bi
2
S
3
, bismutite (BiO)
2
CO
3
and bismite B
2
O
3
. Bismuth metal occurs naturally by itself and is also found as
crystals in the sulphide ores of nickel, cobalt, silver and tin. Its main commercial
source is derived as a byproduct of lead-zinc and copper plants.
Bismuth is used as a metallurgical additive for casting and galvanising, in the
manufacture of low melting solders and fusible alloys. It is also a low toxicity bird
shot and used in fishing sinkers. Additionally, it finds limited application in the
pharmaceutical industry.
B.2.7 Boron
Boron is a non-metallic element and the only non-metal of Group 13 of the periodic
table. More than 200 minerals contain boron but only a few are of commercial
importance. Boron is usually found combined in tincal Na
2
B
4
O
7
10H
2
O (natural
borax), sassolite H
3
BO
3
(natural boric acid), colemanite Ca
2
B
6
O
11
5H
2
O, kernite
Na
2
B
4
O
7
4H
2
O, ulexite NaCaB
5
O
9
8H
2
O and boracite Mg
3
B
7
O
13
Cl. Only four
minerals make up almost 90% of the borates used by industry worldwide: borax,
kernite, colemanite and ulexite.
The most economically important compound of boron is borax, used for in-
sulating fiberglass and sodium perborate bleach. Boric acid is also an important
compound used in textile products. Other uses include synthetic herbicides and
fertilisers, porcelain enamels, detergents, soaps, cleaners and cosmetics, catalysts or
for corrosion control.
B.2.8 Bromine
Like chlorine, the largest amount of bromine is found in the oceans. Salt lakes
and brine wells are also extremely rich sources of bromine. It occurs in Nature as
bromide salts in very diffuse amounts contained in crustal rock.
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