Abstract: An apparatus for estimating a property of an earth formation penetrated by a borehole includes: a carrier configured to be conveyed through the borehole and a gamma-ray detector disposed on the carrier and comprising a scintillation material. The scintillation material includes a barium silicate glass or glass ceramic transparent to light doped with Ce and containing ions of elements with atomic numbers greater than or equal to 55, and having a density greater than 4.5 g/cm3. The apparatus further includes a photodetector optically coupled to the scintillation material and configured to detect light photons emitted from the scintillation and to provide a signal correlated to the detected light photons and a processor configured to estimate the property using the signal.