Al:The average granite out there is under 20 uR/hr gamma, or around .2 or .3 mR/hr if you count all radiation. If you look at it in terms of background radiation, the "safe" granite will double, triple or quadruple your radiation that you get from natural sources all around you. As a granite fabricator, we have a limit of 25 uR/hr gamma, mainly out of concern for our workers.
Radiation exposure is related to the distance from the material. Are these numbers being reported with the geiger counter directly on the granite ... the levels drop substanially since the levels are inversely related to the distance squared. A radiation level 3" from the rock is only about 10% of what it was 1" from the rock.
Do you monitor the radon levels in your plant? You want to install a heat recovery ventilator if your radon levels are high and the source is determined to be from the materials you handle.
In the several homes I have measured for radiation, I found the ceramic tile floor gave off the same background levels as the granite countertop (about 3X what is was in other parts of the homes and that was 1" from the material ... practically nothing).