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Glass is made from sand and limestone. The limestone helps it to be more water resistant. There are different types of glass for different uses:

• heat resistant for cooking and science experiments
• toughened for windows, doors and windscreens
• low energy emitting – to keep the heat in

Glass has also been developed that cleans itself. That’s bad news for window cleaners.

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We should be concerned about the environmental impact of modern gold mining , which uses cyanide and produces vast amounts of toxic waste

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