A topic most people once considered as boring as dirt--rare earth minerals--has fast become a matter of international significance with a direct impact on green technologies and consumer electronics.

Rare earth metals are a group of elements that are used in a wide range of products we use every day, including hard drives and hybrid cars. Their properties, notably as light-weight magnets, make them key to the ongoing miniaturization of electronics and the growth of green technologies.

Rare earth minerals have become a hot-topic issue for industrialists and politicians for one simple reason: supply.

China recognized the importance of these elements decades ago and now supplies almost all the rare earth materials in the world. Companies and countries outside of China are becoming increasingly concerned that this lock on supply could handicap burgeoning green industries, such as wind power and electric vehicles.

In recent weeks, China unofficially created an embargo on the export of rare earth metals, which was lifted last week, perhaps because of international pressure, according to reports in The New York Times. A diplomatic dispute between Japan and China over territory led China in September to temporarily suspend shipments of rare earth elements to Japan, a move that caught the world's attention.

To explain the role of rare earth elements in tech and green tech--and the importance of minerals, in general--we offer this FAQ.

What are these elements and what are they used for Rare earth minerals are a group of 17 elements with properties that make them attractive for certain uses in everything from iPhones to military aircraft. When combined with other common metals, they bring very valuable qualities, such as amplifying light in fiber optic cables or bringing color to TV screens.

The most common use for them is permanent magnets. Certain metals, notably neodymium, have strong magnetic fields, which make them a vital component in electric motors in vehicles. A hybrid car can have about five pounds of rare earth metals in its magnets and battery electrodes. Another use is phosphors, made from yttrium and other metals, which create a pleasing color light in compact fluorescent and LED lamps.

These minerals do the same work of magnets and phosphors in the digital gadgets we use every day, including computer disk drives, smartphones, and flat-screen TVs. Powerful neodymium-based magnets are used in earbud speakers and microphones in small gadgets, while others are used in batteries in cell phones and laptop displays, according to U.S.-based Molycorp Minerals.

Other metals could be used for magnets, for example, but can't match the power per ounce that rare earth permanent magnets offer, particularly in spots where size and weight matters, like cars, consumer electronics, and weapons systems.

Technically, this group of elements is not really rare, although they were thought to be when they were discovered in the late 18th century. However, it is hard to find them in concentrations that are economically viable to exploit.

So why the sudden interest in these metals The interest is not so sudden for many people but these metals have entered onto the geopolitical stage at the highest levels recently, the same way that other vital natural resources have.

Currently, China dominates the rare earth mining industry in terms of production and expertise. It's estimated that China mines about 95 percent of the rare earth metals used in the world today. In the face of price competition from China, mining in other countries, including the U.S., which has significant reserves, has all but shut down in recent years.

But now, supply has become a problem. China sharply reduced its export quotas last year and this year in order to conserve its own resources, according to statements from the Chinese government. That move and the embargoes, have caused a spike in prices and angst around the world.

As the Japanese incident demonstrates, it appears that China is also tightening supply for political reasons, although Chinese officials deny this is the case. Still, China has been transparent about its interest in rare earth elements for a long time, according to Keith Delaney, the executive director of the Rare Earth Industry and Technology Association based in Colorado. China wants to dominate the production of wind turbines, batteries, and other energy technologies and needs to secure its own sources. "They are going to manage their reserves by taking care of their own requirements," he said.

What's being done about alternative supplies Should we be worried There are two rare earth mines outside China--one in the U.S. and one in Australia--that plan to go online in 2012, with others in the pipeline. Molycorp Minerals, which went public earlier this year, plans to reopen the Mountain Pass mine in the Mojave Desert of Southern California, which closed in 2002, and Lynas plans to develop at Mount Weld in Australia. Starting new mining operations is fraught with a number of technical and financial risks and takes between 5 and 10 years to develop, according to experts. Another notable problem for non-Chinese operations is the lack of expertise and an undeveloped supply chain for mineral refinement and production of end-use products, such as magnets.

Rare earth metals are particularly challenging to extract because they are often found together and it requires a lot of chemistry and metallurgy to separate them from each other and purify them. These mines also typically contain radioactive thorium, which has to be handled separately. Molycorp claims that its current water-based process for mining and extraction will be far cleaner than previous operations at Mountain Pass.

But even if these operations come online flawlessly, it's unlikely that the supply will be able to meet the demand in the very near future, said Delaney. The best the world can hope for is a smooth transition when new mines open in 2012, he said.

For electronics, it's not a very acute situation because computers and phones use just a few grams of the material per unit. But it's a totally different story for vehicles, where the scale is kilograms, and wind turbines, where it's hundreds of kilos.

The most promising technology in wind power to come along in recent years is direct drive turbines, which use permanent magnets to improve the reliability and cost of generating electricity. Every megawatt of wind power requires about half a ton of permanent magnets, said Delaney. To meet the projected future demand for wind--where 10,000 megawatts of capacity were installed in the U.S. last year--there just isn't the supply, he said.

What about recycling At this point, recycling of rare earth metals is not done in a significant way, according to a United Nations report from earlier this year. But there are signs that this is starting to change, notably in Japan, which needs to import rare earth metals. A Japanese town has started an "urban mining" project to extract valuable metals, including gold and rare earth magnets, according to a report in The New York Times.

A neodymium-iron-boron (Nd2Fe14B) permanent magnet.

Many people believe that recycling rates should be increased on all manner of valuable metals, given the constraints on supply for rare earth elements and many other raw materials, such as the indium used in solar cells, semiconductors, and LED lights. Toyota last week launched a nickel recycling operation where used nickel-metal hydride hybrid batteries will be repurposed. Recycling is also far less polluting than extracting raw materials.

"Recycling is definitely going to be a big part of the solution to this problem," Alex King, director of the U.S. Department of Energy's Ames Laboratory in Iowa, told Scientific American. The lab is seeking to develop alternative processes to prepare neodymium-iron-boron magnets, which can be sourced in the U.S.

What's next On the political stage, it's safe to say that control over rare earth metals will remain in the news in the years ahead. The challenge isn't only the concentrated supply of the raw materials in China, but the location of the entire supply chain that goes with it. "China is the center of the world rare earth industry, in all of its aspects," said rare earth metal expert Jack Lifton during a trip to China earlier this year.

Other countries are clearly waking up to this issue. Last week in Washington there was a conference held specifically on this topic and there have been a number of Congressional hearings, particularly about how rare earths relate to green technologies and the military, which relies on them in many applications. As an indicator of corporate interest in rare earth metals, both General Electric and General Motors are members of the Rare Earth Industry and Technology Association.

The general public, obviously, is less engaged on this issue, but media coverage of rare earths is growing. In general, as people look for alternatives to fossil fuels with green technologies, the issue of raw materials is becoming more prominent. Although it's not part of the rare earth metals group, the source and supply of lithium for batteries, for example, has come under sharper focus.

At last week's conference, political officials from the U.S. and Germany voiced alarm over China's control over supply. German officials have appealed to the European Commission and the World Trade Organization to intervene on China's moves to restrict supply.

In the meantime, new mines can't come online fast enough. "The mood at (last week's) conference was that this is a solvable problem," said Delaney. "Whether we have time to solve it is the issue."