This chapter outlines the applications of critical minerals in science and engineering, focusing on antimony, beryllium, bismuth, cobalt, magnesium, tantalum, niobium, titanium, and tungsten. Antimony is widely used in flame retardants but needs better recycling due to environmental concerns. Beryllium offers high strength and low weight for aerospace and medical uses, though toxicity requires strict safety. Bismuth finds roles in medicine and cosmetics, while cobalt is vital for EV batteries, highlighting sustainable sourcing. Magnesium’s strength-to-weight ratio supports automotive and aerospace applications. Tantalum and niobium enable advanced electronics and superconductors. Titanium’s strength, low weight, and corrosion resistance make it indispensable for aircraft and spacecraft. Growing reliance on these minerals underscores the urgency of sustainable extraction, circular economy practices, life cycle assessments, and mitigating environmental impacts.