Is our granite inspection table harmful?

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Jbcourt
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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
 
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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.
 
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.