Bismuth Germanate (Bi₄Ge₃O₁₂), commonly known as BGO, is a high-density inorganic scintillator valued for its exceptional gamma-ray stopping power. Key specifications include: very high density (7.13 g/cm³), providing the highest photo-fraction among common scintillators; high effective atomic number (Z=75), making it extremely efficient for gamma-ray photoelectric absorption; excellent chemical resistance and mechanical durability; non-hygroscopic, requiring no hermetic packaging unlike NaI(Tl); and a refractive index of 2.15. BGO is the preferred scintillator for applications requiring maximum detection efficiency in compact volumes, such as Compton spectrometers, PET scanners, and high-energy physics calorimeters. Important supply note (2025): Chinese export restrictions on bismuth, germanium, and other heavy elements have constrained BGO crystal availability, particularly for large sizes. Raw material costs are rising, and some manufacturers have temporarily limited large-format BGO production. Contact Berkeley Nucleonics for current BGO availability and alternative scintillator recommendations.