China has raised worries about supplies by curbing exports, notably to Japan but also to the United States and Europe, renewing interest in finding sources in other countries.

All are likely to face tougher environmental laws than China. Workers at Baotou, which calls itself the "capital of rare earths" 650 km (400 miles) west of Beijing, tend cauldrons of sputtering acid and ore amid acrid fumes.

"There is no question that the costs of environmental compliance in the U.S. are significantly higher than in China," said Jim Sims, spokesman of Molycorp Minerals LLC, the main U.S. producer from stockpiled ore at Mountain Pass, California.

"That has provided the Chinese with a significant price advantage in rare earths. But that has changed," he said.

He predicted that Molycorp, planning to resume production with a new, cleaner process in 2012, could mine at a cost of $1.26 per pound (0.45 kg) averaged across all earths, against $2.54 as the firm's best estimate for Chinese production.

"Some ores have a lot of thorium. We are blessed with a very low level...We have a protocol for handling it and it's then shipped to a storage facility," he said.

"The Russians and the Indians have a relatively higher percentage of thorium," he said. Mining was halted at Mountain Pass in 2002 partly after a wastewater leak from a pipeline.

Eoin Treacy's view Rare earth metals have caught the imagination of investors as the necessity of these materials in the manufacture of high end technologies is more widely realised. China restricting supply and subsequent price rises have helped fuel speculation. Many have questioned how Western governments could be so short sighted as to allow China a virtual monopoly of such strategic resources. However, it is not so difficult to appreciate.

Extraction of the necessary ore and the smelting/fabrication process for these metals is costly, energy intensive, hugely polluting, subject to a raft of regulations and potential litigation, not to mention the "not in my back yard" attitude prevalent in many countries. China on the other hand has followed a deliberate policy of crowding out higher cost producers and appeared to offer cheap, abundant supply without the headache of similarly stringent environmental regulations. The result has been a shuttering of global production and total Chinese dominance of the sector.

The status quo was undisturbed for decades but China is quickly moving up the value chain in manufacturing and is quickly gaining a dominant position in green technologies such as renewable energy. Domestic demand for rare earth metals, whilst negligible 20 - 30 years ago is now ramping upwards. Logically, China will now seek to supply the domestic market before exporting to third parties. Many have speculated that they will also encourage foreign companies to relocate to China in return for privileged access to rare earth resources among other incentives.

Consolidation of recent gains is a common theme among this list of 20 rare earth metal miners. The better performers had raced to impressive highs but all have now pulled back; some more severely than others. If the medium-term bullish outlook is to be sustained, a number of the leaders such as Lynas Corp, Alkane Resources, Rare Element Resources, Inner Mongolia Baotou Steel Rare-Earth High Tech and China Rare Earth Holdings will find support in the region of their 200-day MAs prior to reasserting their uptrends.