Metals, their Biological Functions and Harmful Impacts - Mining and the Environment: From Ore to Metal - page 488

Half-life

4.5 billion
years

Uranium 238

Alpha

24.1 days

Thorium 234

Beta Gamma

1 minute

Protactinium 234

Beta Gamma

245,000 years

Uranium 234

Alpha Gamma

76,000 years

Thorium 230

Alpha Gamma

1,600 years

Radium 226

Alpha Gamma

3.8 days

Radon 222

Alpha

3.0 minutes

Polonium 218

Alpha

27 minutes

Lead 214

Beta Gamma

20 minutes

Bismuth 214

Beta Gamma

160 micro second

Polonium 214

FIGURE 11.5
Uranium Decay Products and their
Half-Lives

Alpha

22 years

Lead 210

Beta Gamma

5 days

Due to the continuous production of
radon from the decay of radium-226,
radon presents a long-term hazard
that continues long after uranium
mining ceases. When radon gas is
inhaled, radon progeny are also inhaled,
resulting in a much larger dose of alpha
radiation to the lungs than would be
delivered by the gas alone.

Bistmuth 210

Beta Gamma

138 days

Polonium 210

Alpha

Lead 206 Stable

Alpha

*Microsec: 1/1,000,000 of a second **Millisec: 1/1,000 of a second

11.3 METALS, MINERALS AND ROCK

Metals do occur as single elements in nature (termed 'native' form). Gold is an obvious
example; mercury is another. More often, however, they occur in combinations of two
or more elements to form a mineral (for a list of common minerals targeted for mining
see Chapter Five). To be classii ed as a mineral scientii cally, a substance generally must
meet i ve requirements (Eby 2004): it must be naturally formed; it must be solid; it must be
inorganic; it must have a specii c chemical composition; and it must have a characteristic
crystal structure. A mineral always contains the same elements in the same proportions
by weight. Interestingly, a mineral has quite different properties from its constituents.