Over 15 years, he returned 70 times with a metal detector built for gold prospecting.

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Bud Guthrie, an amateur gold hunter, found it while prospecting with his metal detector in 1989 in a Colorado River canyon.

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Alongside this experiment, another large detector - LUX - which is in a gold mine in South Dakota in the US will soon be coming online.

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He told Australian media the prospector had been using a state-of-the-art metal detector, which meant he was able to find the gold relatively deep underground in an area which had been searched many times in the past.

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