What makes identifying minerals difficult even with a key?

The infrared (ir) and the ultraviolet(uv) represent the two extremities of the visible spectrum (400-700nm). while ir represents electromagnetic radiation with wavelengths longer than those of visible light, uv represents wavelengths shorter than visible light

Bidk

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey