The Periodic Spiral assigns the color yellow-green to oxygen, zirconium, ruthenium, cadmium, and tellurium. Oxygen under excited conditions is responsible for the typical brilliant yellow-green (and much rarer bright red) colors of the Aurora. Ruthenium, a platinum metal, has a distinct yellow-greenish tinge. Cadmium is the basis for pigments of greenish yellow hues (as well as orange and red). The reaction of iodine trichloride with tellurium in a sealed evacuated glass ampoule at 250C yields yellow-green, moisture sensitive crystals of TeCl4.