What is the thinnest material that can block gamma rays?

Question

My question is basically what is the thinnest material that could block gamma rays/radiation. I already know that a lead/concrete mix could do it but it would be too thick to actually be useful, is there any other material? Possibly one of those new meta-materials?

Thanks

Answer 1

Nothing blocks gammas. Lead/concrete only attenuate gammas. I don't know what more can be said, only that gammas are the most energetic EM waves known. They represent the most violent activity in the universe, and at staggering temperatures.

Answer 2

Lead shielding works about the best.  Other heavier elements like uranium are marginally better, but their cost usually precludes their use.

Answer 3

Aluminum Foil