Travertine has some of the same issues as marble does when it comes to scratching. As a type of highly porous limestone, travertine is extremely soft when it comes to durability. It is primarily made of calcite, which only has a 3 rating on the Mohs scale of hardness. This means that a knife blade, which has a rating of 5.5, could easily cut into the stone. Another source of scratching on travertine comes from etching, where the stone is exposed to acidic content. Many common kitchen products are slightly acidic, and if they are spilled on the stone they will quickly eat away at its surface. For this reason, travertine is not recommended for kitchen countertops.