Ключевые слова: 59, chemical, chemical element, chemistry, earth, electronics, element, expensive, geology, grey, handful, high purity, highly pure, industrial, industry, lack, material, metal, metallic, mine, mineral resources, mining, nature, periodic table, pile, pr, praseodymium, pure, rare, rare earth, rare earth element, rare earth metal, rare earth mineral, rareearth elements, raw material, ree, resource, scarcity, science, silver, symbol, very pure,