Shares in WA rare earths miner Lynas have plummeted after a Malaysian Court delayed the start of production at its plant to consider an application by opponents.
Lynas had planned to finally begin operations at the rare earths processing plant this month, following a long saga, but will now wait until at least November after the Kuantan High Court extended an interim stay on the licence.
Environmental activists and local residents oppose the plant on the grounds that it will produce radioactive pollution that will seep into ground and water.
Lynas shares closed down 13 cents, or 16 per cent, to 73 cents.
Malaysia's Atomic Energy Licensing Board awarded a temporary operating licence to Lynas last month.
However the Save Malaysia Stop Lynas opposition group are seeking a judicial review of that decision by Malaysia's Minister of Innovation, Science and Technology.
The court will decide whether to suspend the operating permit pending a judicial review on November 8.
The plant on the country's east coast would be the biggest rare earth plant outside China and is considered important to breaking that country's current 95 per cent monopoly on global supply.
Lynas insists that any radioactive waste would not be harmful to humans, having chosen the site because it was cheaper and it had thought easier to build politically than in Australia.
Mitsubishi is still cleaning up the site of a rare earth processing plant it closed in Malaysia in 1992, which some residents say has caused health problems including birth defects and cancer.
Lynas's Mt Weld mine near Laverton is considered the world's richest deposit of rare earth minerals, which have a range of hi-tech uses such as in hybrid cars and computers.