REUTERS - Rare earth elements have become essential components for building smartphones, wind turbines and electric cars. Before manufacturers can use the material extracted from the ground, it must go through a complex and expensive process.

Ren Limin, a worker at the Jinyuan Company's smelting workshop, watches over pots containing the rare earth metal Lanthanum before he pours it into a mould near the town of Damao, located in China's Inner Mongolia Autonomous Region October 31, 2010. REUTERS/David Gray/Files

“There is a reason why the rare earths are called rare. They’re not called rare because they’re truly rare. They’re called rare because it’s very difficult to isolate these elements individually and it takes a lot of skill to do that,” said Constantine Karayannopoulos, chief executive of Neo Material Technologies, a Toronto-based rare earth refining specialist.

Here is a step-by-step description of the process, followed by a list of valuable rare earths and their current prices:

* The first step is to mine the ore, usually a cabonatite or monazite, that contains the rare earths. Depending on the grade, it could take anywhere from 6 to 86 tonnes of ore to produce a single tonne of rare earth mineral.

* Next the material goes to a chemical plant for separation. This step, called “cracking,” usually involves using acid or heat. The product that comes out is a rare earth concentrate, containing all 17 rare earths mixed together. Cracking can also result in byproducts like tantallum, zirconium or radioactive thorium.

* Rare earth concentrate must then go to another facility where it is separated into individual rare earths that are refined into oxides. Separation is done by atomic weight, starting with cerium, the most abundant rare earth. To get valuable dysprosium, for example, the less valuable rare earths that come before it on the periodic table must first be separated out. To get terbium, it takes more than 30 days of processing.

* Next the rare earths are treated through a process, called benefication, that produces high-value oxides, metals or magnetic powders. These products are made to the specifications of each manufacturer. An oxide made to the specifications of one customer might not suit another’s needs.

* Finally, the rare earths are put into the end product, whether it is a permanent magnet for a wind turbine, or a high-efficiency lightbulb.

VALUABLE RARE EARTHS

NEODYMIUM - A light rare earth that is the main ingredient in permanent magnets, used in car motors, wind turbines, smartphones and other technology applications. It is also used in speakers, earphones, hard drives and ceramics. While neodymium is more readily available than heavy rare earths, analysts forecast a tight supply well into the future.

Current price: $80 a kilogram.

PRASEODYMIUM - Another light rare earth that is used in permanent magnets, strengthening metals, glass coloring and ceramics.

Current price: $76/kg.

DYSPROSIUM - A heavy rare earth that is used in permanent magnets, lasers and nuclear reactors.

Current price: $286/kg.

TERBIUM - A heavy rare earth used in fluorescent lights, fuel cells, permanent magnets and LCD screens.

Current price: $615/kg.

EUROPIUM - A heavy rare earth used primarily in LCD screens.

Current price: $605/kg.