Bertrandite is a mineral composed primarily of beryllium, aluminum, and silicon, with the chemical formula Be4Si2O7(OH)2. It typically appears as a colorless to pale yellow or greenish crystal and is often found in metamorphic rocks. This mineral is an important source of beryllium, which is used in various applications, including aerospace materials and electronics. The name bertrandite honors the French mineralogist Henri Bertrand, who studied the mineral in the 19th century. It is commonly located in regions with volcanic activity, such as Brazil and the United States. Due to its rarity, bertrandite is of interest to both collectors and researchers in geology.