What is REE?

The rare earth elements (REE) are a set of seventeen metallic elements.
These include the fifteen lanthanides on the periodic table plus scandium and yttrium.
Rare earth elements are an essential part of many high-tech devices. Rare-earth elements (REE) are necessary components of more than 200 products across a wide range of applications, especially high-tech consumer products, such as cellular telephones, computer hard drives, electric and hybrid vehicles, and flat-screen monitors and televisions.
Although the amount of REE used in a product may not be a significant part of that product by weight, value, or volume, the REE can be necessary for the device to function. For example, magnets made of REE often represent only a small fraction of the total weight, but without them, the spindle motors and voice coils of desktops and laptops would not be possible.

The REE: definitions

The individual REE are difficult to separate, and so it was not until the 20th century that all of the REE were identified. This difficulty in separating the REE led to the misleading name ‘rare earth’; the REE are actually relatively abundant in the Earth’s crust, with a total concentration of about 180 ppm in bulk continental crust (Rudnick and Gao, 2003).

The REE are typically divided into two groups based on their atomic weights: (1) the light rare earth elements (LREE), which are here considered to include the elements lanthanum to samarium, and (2) the heavy rare earth elements (HREE), which here include the elements europium to lutetium, plus yttrium. The elements from samarium to terbium are sometimes described as the middle rare earth elements (MREE). The REE are mainly trivalent (Ln3+), although cerium and europium can occur naturally in different oxidation states. Their trivalent electron configuration explains why the REE readily substitute for one another in mineral structures, and also gives them some of their more unusual magnetic and optical properties.
According to EURARE Project

The main part in concentrate is lanthanides 97,17 %(La2O3 – 22.4%, Ce2O3– 50.02%, Pr2O3 – 4.22%, Nd2O3 – 20.05%)