The brittle bluish-white metallic element you are referring to is most likely Bismuth (Bi). Bismuth is a chemical element with the atomic number 83 and is known for its distinctive bluish-white color. It is a brittle metal that can be easily broken or crumbled. Bismuth is also known for its low thermal and electrical conductivity. It is often used in various applications, including cosmetics, pharmaceuticals, and alloys.