Gadolinium oxyorthosilicate (known as GSO) is a type of scintillating inorganic crystal used for imaging in nuclear medicine and for calorimetry in particle physics.

The formula is Gd2SiO5. Its main properties are shown below:

Density (g/cm3)6.7
Melting Point (°C)1900
Radiation Length (cm)1.38
Decay Constant (ns)50-60
Light Yield (relative BGO=100%)110
Index of Refraction1.87
Peak Excitation (nm)350
Radiation Hardness (rad)>106
HygroscopicNo