You can't date the beads themselves. Or you could, but you'd get the date when the rock formed, which is potentially a few million years ago, not the date when

You can't date the beads themselves. Or you could, but you'd get the date when the rock formed, which is potentially a few million years ago, not the date when the beads were polished by some jewelers into their current shape. With the twine, you get the date when the carbon was metabolized, which is when the plant or animal where the fiber came from was alive and breathing. This is very close in time to the date when the fiber was actually twisted to form the twine, and to the date the twine was coupled with the beads to form a necklace or pendant.