In a supply risk index of chemical elements that are of economic value, four elements placed ahead of rare earth metals.
British Geological Survey compiled the elements in a risk list published in 2011.
Antimony, tungsten, mercury and platinum group metals had a relative supply risk index rating of 8.5 while rare earth elements were ranked at 8.0.
Except for PGM, the leading producer of these four elements was China. The lead producer of platinum group metals is South Africa.
"The risk list highlights a group of elements where global production is concentrated in a few countries," writes the report's authors.
"The restricted supply base combined with the relatively low political stability ratings for some major producing countries significantly increase risk to supply."
The author's the list focuses on risk to supply. The demand side, where substitution can play a role, is not considered.
