As a result of weathering, they have a thin patina or surface layer in which some of the feldspar has been turned into clay, resulting in a softer material, rated 3 to 4 on the Mohs scale of mineral hardness, which can be scratched.
They have a thin patina or surface layer in which some of the feldspar has been turned into clay. This was as a result of weathering. They was resulting in a softer material. This was as a result of weathering. A softer material was rated 3 to 4 on the Mohs scale of mineral hardness. Mineral hardness can be scratched.