A tonne of ore from a gold mine produces just 5 grams (0.18 ounce) of gold on average, whereas a tonne of discarded mobile phones can yield 150 grams (5.3 ounce) or more, according to a study by Yokohama Metal Co Ltd, another recycling firm. The same volume of discarded mobile phones also contains around 100 kg (220 lb) of copper and 3 kg (6.6 lb) of silver, among other metals.

Urban miners look for precious metals in cell phones – Yahoo! News