Silver mining company shares plummeted more than 10 percent Tuesday after Greece announced a referendum on whether to accept $180 billion of bailout money.

The surprise announcement stunned global markets, which have endured two years of watching Europe's sovereign debt crisis morph from a Greek problem into a global financial threat.

Last week European leaders announced a comprehensive plan to fix the crisis, including giving Greece $180 billion, on condition of further austerity. The news was hailed from Athens and around the world.

But early Tuesday Greek Prime Minister George Papandreou stunned global markets by saying Greece will hold a referendum in January on whether it wants to accept the $180 billion - and the additional austerity it requires.

That news chopped Asian stock markets more than two percent, European stock markets more than five percent and U.S. stock markets more than two percent.

Among the hardest hit were banks and commodities, particularly mining company stocks.

At the forefront of the mining company share crash were silver miners.

In mid-morning trading, First Majest Silver Corp. plunged 11 percent, Coeur d'Alene Mines Corp. fell 8.4 percent, Great Panther Silver Ltd. was down 10.8 percent, Mag Silver Corp. lost 9.3 percent and Silvercorp Metals Inc. dropped 10.3.

Silver exchange-traded funds were also sharply lower: Global X Silver Miners fell 8.6 percent.

The price of silver for December delivery fell four percent on the Comex.