Get Mark Smith talking about his company's biggest asset and the feeling is one of being transported back to a high-school chemistry class. Cerium, lanthanum, praseodymium, neodymium . . . The mine described by the head of the Denver-based Molycorp Minerals contains deposits featuring some of the more esoteric reaches of the periodic table.
"It is really a challenge to explain to investors what we do," Mr Smith concedes.
Yet these so-called minor metals and rare earths are as critical as copper and aluminium to the global economy. From the cobalt in mobile phone batteries to the neodymium in Toyota's hybrid Prius cars, "minor metals and rare earths are involved in every aspect of modern life", says Guy Darby of the London-based Minor Metals Trade Association.
Take cars. At the start of the 20th century they were typically made up of about five raw materials: wood, rubber, steel, glass and brass. But today, according to a report by the National Academies, which has been written by experts who advise the US on science and technology, "a typical automobile may contain up to 39 different minerals in various components" - including several obscure metals.
That increased demand has pushed prices up, with many types trebling or more in value in the past five years. With China dominating much of the supply, and with its own industry's demands to satisfy, policymakers and business in the west have started to worry about future availability. The National Research Council of the US, another scientific group, after studying the market in 2007 concluded that the reliance on foreign sources could "expose a range of US industries to political, economic and other risk".
The result: raw materials as little-known as terbium, samarium and ruthenium are starting to command a level of attention once reserved for energy and food security. "Rare earths are to China as oil is to the Middle East," Deng Xiaoping proclaimed when he was leader as far back as 1992.
With volumes still small, even rumours of tiny variations in supply or demand can send prices up or down by a factor of 10. But because the overall trend is upward, China faces the prospect of losing its total grip as the increase in prices makes other countries' production more viable economically than before. Molycorp's Mountain Pass mine, which sits on the California-Nevada border, was shut in 2002 when prices plummeted as Chinese production flooded the market. Now, Mr Smith says it could be reopened.
The growth of "green technologies" such as wind turbines is also expected to boost the sector. The environmental applications of rare earth elements "have increased markedly" over the past 30 years, according to the US Geological Survey, a government agency, which expects the trend to continue. Avalon Rare Metals, a Toronto-listed mining company, reckons that about 25 per cent of new technologies rely on minor metals and rare earths.
"Minor" metals and "rare" earth elements owe those designations more to a lack of familiarity than true scarcity. Some, including manganese, are as common as base metals such as nickel or precious metals such as gold. However, as the US Geological Survey notes, in contrast to ordinary base and precious metals, minor metals and rare earths are so dispersed that production is feasible only in the few places where they are present in high enough concentrations.
Mostsupply thus comes from a handful of mines. Bayan Obo, in the Chinese region of Inner Mongolia, is the world's largest, followed by Mountain Pass, then Mount Weld in Australia. Like Mr Smith's facility, Mount Weld is currently inactive, though production there is also likely to restart.
So in a world in which Beijing's voracious appetite for commodities dominates demand trends, China is also the main, if not only, supplier of a number of those little-known metals. In particular, it accounts for 97 per cent of the global supply of rare earth elements - a list of 17 elements of the periodic table for which demand is growing fast.
China's supremacy, together with quotas placed by Beijing on exports over the past few years amid rising domestic demand, has triggered concerns about long-term supplies. Dudley Kingsnorth, an independent analyst who is widely followed in the industry, is one of the experts who reckons the squeeze could come in the next five years.
Concerns about China's dominance were aggravated by market rumours late last year that Beijing was about to tighten its rare earth elements export quota further, extending a policy that has seen a notable cut in exportable quantities in the past decade. However, the traders' chatter proved false: Beijing eased its quotas recently, allowing exports of 16,300 tonnes of strategically important rare earth metals for the first half of this year, up by more than 8 per cent from the same period in 2009.
Wang Caifang, deputy directorgeneral of China's Ministry of Industry, told an industry conference last year that Beijing would not take "arbitrary" decisions. "All our decisions will be consistent with scientific development," she said. "China will not close its doors."
Such reassurances are not enough to ally the concerns of US politicians such as Mike Coffman, a congressman who has pushed for new legislation to minimise American dependence on foreign supplies of obscure metals. "This is strategically dangerous," he has argued.
Yet all is not quite as it may seem. More and more more western companies have been shifting production to China in order to bypass the quotas, as the limits apply only to the ores and not to finished products such as magnets or batteries.
Indeed, some see the export quotas as an attempt by Beijing to accelerate that trend, with companies relocating near its mines in Inner Mongolia. China, they say, is not clamping down on supplies as part of a resource war but is attempting to move value-added industry into the country in order to profit from the presence.
"China does not want to supply rare earth to build a Prius or Volt car battery: it wants to build and market the vehicle," says Anthony Lipmann of Lipmann Walton, a UK-based trader.
China has two other reasons to tighten its grip. For one, Beijing is trying to clamp down on illegal, unsafe and polluting mining across all commodities. Paradoxically, mining rare earth elements - crucial for a number of green technologies - is potentially damaging for the environment. Also, prices have not risen as much as Chinese miners had hoped; the country's policymakers believe that restricting supply will push prices up, traders say.
In comparison with earths, demand for minor metals is less beholden to China, traders say. For some - such as titanium, rhenium or lithium - Beijing is not even the dominant supplier, with Chile, the US, Congo, Australia and Russia being large producers too. So investor enthusiasm has centred on rare earths over the past two years, fuelled by the mining companies themselves warning of looming shortages. That bubble burst late last year.
Policymakers remain worried, however. Japan is already stockpiling obscure metals. The European Commission is considering a list of "critical" minor metals and an announcement, including measures such as stockpiles, is expected later this year.
With mining industry lobbyists pushing for strategic stocks, the US defence department has discussed creating a similar list. "This is because they [minor metals] have a number of high-tech applications that are important for the economy and because they are marked by a higher degree of supply risk than the more traditional base and ferrous metals," says the National Academies' report.
In response, some companies that need minor metals and rare earths are supporting exploration and production, in order to diversify their supply base and keep prices low. Toyota Tsusho, an affiliate of the Japanese carmaker, for example this month announced a deal with Australia-based Orocobre to help develop lithium deposits in Argentina. The metal is needed for use in hybrid cars' batteries.
Many traders remain sceptical, arguing that political concerns about so-called "critical" metals are misplaced. They do not foresee worse shortages than for more common commodities such as iron ore.
As Mr Lipmann points out, this is not the first time that policymakers worrying about metal supplies have fumbled their response. He remembers how the US considered tin a critical metal at some point. It even built a stockpile because of fears that communism would spread from the Korean peninsula to important producing nations including Indonesia, Thailand and Malaysia.
At its peak in 1972 the stockpile contained 250,000 tonnes of the metal, equal to more than the world's entire annual supply at that time. "The US government then spent the next 30 years trying to get rid of it without disrupting the market," Mr Lipmann recalls.
Now, the worry is again that governments will commit the same mistake as they seek to limit a national dependency on China for supplies of substances that, while less prosaic than tin, are needed in rather more modest volumes.