But it cannot distinguish between carbonates and sandstone as they both have similar deflections on the gamma ray log. Thus gamma ray logs cannot be said to make good lithological logs by themselves, but in practice, gamma ray logs are compared side-by-side with stratigraphic logs.
The gamma ray log cannot differentiate between carbonates and sandstone due to their similar deflections, rendering it unsuitable for accurate lithological identification.  However, gamma ray logs are often compared with stratigraphic logs in practice.