Several German tourists have turned up in the remote town asking for directions and demanding to see their stake, only to be told they have been conned.

Had they carried out even the most cursory checks, however, they would probably have smelled a rat.

Whoever was behind the scam could not even get the name of the town right, instead referring to 'Cooper Pedy'.

Coober Pedy's Mayor, Eric Malliotis, said the bewildered Germans who turned up in town, certificate in hand, were a laughing stock.

'Too many suckers are born every second. It's a con job. A smart person has thought they can make money from idiots,' Mr Malliotis said, adding it would be physically impossible to mine such a small plot.

'It's a different thing if you buy shares in a mining venture where you get a certain percentage, but not square metres of area.'

Internet and magazine advertisements in Germany claimed the tiny plots were a good investment because mining licences had tripled in the past two years.

'The mines at Cooper [sic ] Pedy are like a magnet attracting people. Now you, too, can buy a licence to dig for 10 years,' the advertisements read.

The only thing the ads got right was claiming that Coober Pedy, which lies in desert half-way between Adelaide and Alice Springs, is the opal capital of the world.

Australia produces 95 per cent of the world's opal and much of it comes from the isolated township. Opals have a milky appearance, dappled with vivid swirls of colour.

Police in South Australia have investigated the scam but say they are unlikely to take any action.