Calomel Calomel is a mineral that shines bright but demands caution. Calomel stands out for its brilliance and fluorescence, yet its mercury composition makes it hazardous, reminding us that not all minerals are as harmless as they appear. Calomel is a white halide mineral with an adamantine lustre. It shows conchoidal fracture and sectile tenacity. It commonly forms as a secondary mineral in mercury deposits and exhibits strong fluorescence under ultraviolet light. Due to its mercury composition, calomel is toxic and environmentally hazardous. Amazing Fact Calomel contains mercury, making it both scientifically important and potentially dangerous to the environment. Source: Geological Survey of India