Earlier, in La Paz, Bolivia's mining minister said mining unions were asking the state to "recover" the silver, zinc, lead and tin mines currently operated by private companies, in line with President Evo Morales' drive since 2006 to regain control over key natural resources.

"The shares are down because there is a fear that the Bolivian government would potentially take possession of more mines," said Joe Cusick, senior market analyst at Chicago-based brokerage firm optionsXpress.

"The concern is that they are going to take possession for public use and then potentially divest the private ownership.

"In Pan American Silver, the risk is that these state mining companies would rescind some of their contracts."

Tony Ebersole, a spokesman for Coeur, said the company's property rights are not the subject of expropriation.

Eoin Treacy's view Bolivia, under Evo Morales, has demonstrated a willingness to nationalise oil related assets in the past and with prices for industrials commodities and precious metals close to new nominal highs attention appears to be refocusing on those sectors. Bolivia does not have a functioning stock market, but a number of foreign miners with interests in the country have pulled back sharply over the last week.

Coeur D'Alene and Pan American Silver are perhaps some of the most exposed. However, progressions of higher reaction lows remain intact for both shares and they would need to sustain a move below their respective 200-day MAs to indicate that a medium-term peak have been reached.

Silvercorp Metals (China & Canada), Silver Wheaton (no exposure to Bolivia), Fortuna Silver Mines (Peru & Mexico), Endeavour Silver Corp (Mexico), First Majestic Silver Corp (Mexico), Silver Standard Resources (Peru), Hecla Mining (USA) and Fresnillo (Mexico) all also pulled back somewhat this week but have no exposure to Bolivia and silver continues to hit new highs.

A number of these shares do have exposure to Peru which has also suffered from speculation that nationalisation will be a priority for the Humala government if elected. The Lima Index pulled back sharply this week but retraced yesterday's decline and improved on that performance today, marking a low of at least near-term significance. The Index will need to hold above yesterday's low and find support above it on a reaction to indicate a nadir of medium-term significance has been reached. The iShares Peru MSCI All Peru Capped Index Fund has tracked the market reasonably well