* Highly reactive: Europium is very reactive and readily oxidizes in air, meaning it quickly reacts with oxygen to form an oxide. This oxide layer gives it a dull gray appearance.
* Rarely seen pure: Because of its reactivity, you'll rarely see europium in its pure, metallic form. It's usually found in compounds like europium oxide (Eu2O3), which has a pale yellow or white color.
So, although europium itself is silvery-white, you're more likely to encounter it in its oxide form, which appears pale yellow or white.
