Can you detect betas? I have a counter with a mica window that easily lets betas and even alphas in.
I get pretty different results checking a 5g U sample, which is sealed under Ar in a glass vial.
Background is 31 +/- 4 counts per minute, when I place the vial with the U next to the geiger counter, I get 12360 +/- 80 counts per minute. About 400 times as high.
I believe that Geiger counters are far more sensitive to betas than gammas (detecting c. 100% vs 1 or 2% of incident particles). I suspect that the radiation from my U is mostly betas from Pa-234 decay (no alphas get through the vial), vs background which is entirely gammas, so the relative increase in radiation is not nearly as large, but it still seems like a dramatic difference.