Is our granite inspection table harmful?

[Jbcourt]

A pink granite inspection table here where I work comes up radioavtive when read with
a gieger counter. The Geiger counter says beta emissions are coming from this table. When I scan the gray granite table the geiger counter reads almost nothing.

Note: I don't know the level of radiation. The geiger was not mine.

I think the potassium feldspar in the Pink granite table must be source of the emissions?


Questions:
1. If it is the potassium, what isotope could it be?
2. If its not potassium then what could it be?
3. Can it hurt us

[PLAIN]http://americancomputerservicing.com/images/potassium_feldspar_in_granite.jpg

[PLAIN]http://americancomputerservicing.com/images/gray_granite.jpg

 

[mathman]

K-40, which occurs naturally, is radioactive, but has an extremely long half life - 1.277E+9 years. It is not dangerous.
Some rocks (I am not that familiar with which) also contain Uranium. Although U-238 is an alpha decay isotope, some of its daughters are beta decays.

 

[D H]

Apparently the problem isn't so much the radiation given off directly by the uranium in some granite countertops -- it's the radon that is a by-product of the uranium decay.

You can get home radon testing kits for a fairly small price ($30 or so).They might tell you to gut your kitchen ASAP, but they might also tell you there is nothing to worry about.