As a rule, the strongest window sills are made of traditional granite, because it is recognized as the hardest. But this natural material can be adverse for health, because it can accumulate radiation. During the purchase of material for your window sill, you should certainly study the radiation safety certificate, the material should be at least 1 security group. Although in terms of radiation is much safer marble. It can be of a variety of tones and flowers, starting with simple white and completing the darkest. Smarts made of marble and granite imported from Italy are very beautiful. In its structure, onyx stone is especially similar to marble, although it stands out because it can miss the light. This can create an unusual, outstanding and magnificent reflection. Of course, the onyx stone is not of cheap natural materials: 1m2 can cost about $ 420. It must always be remembered that any material needs a careful attitude. We must not forget that the smooth surface of any stone is very easy to damage in any way, in this regard it is necessary to be especially accurate.